Mergers and Acquisitions Examples: The largest company M&A deals list

When it comes to mergers and acquisitions, it’s a well-known fact that if everything is equal, then it stands to reason that the more money that’s involved in a merger or acquisition, the higher the chances are that a company is overpaying for a target company. However, despite how you feel about mergers and acquisitions of this size and scale, it’s a fact that we can’t afford to turn a blind eye to. Take a look at our list of the biggest M&A failures for examples of why.

As a company, DealRoom has been able to assist many businesses in their quest for change and success in mergers or acquisitions. And so, we’ve put together a list of some of the biggest mergers and acquisitions in history.

In this article: 

• Biggest mergers and acquisitions examples list
• Lessons from successful and failed mergers and acquisitions
• ‍Frequently asked questions
• Final thoughts

Related: Recent M&A Deals and 8 Biggest M&A Deals in History (so far) and 8 Biggest Upcoming M&A Deals in 2023 (so far)

Biggest mergers and acquisitions examples list

Well, from this list alone, it would appear that the biggest mergers and acquisitions are doomed to fail - or at least fail for their shareholders. However, as you’re no doubt aware, this isn’t the case. Indeed, some of the biggest mergers and acquisitions in the last 30 years have been a huge success.

As a matter of fact, a great deal of these mergers and acquisitions that have taken place in the past have been successful in achieving what they initially set out to do when the merger or acquisition was first made.

So, with that said, let’s now take a look at 35 of the biggest mergers and acquisitions that have ever taken place in the world.

1. Vodafone and Mannesmann (1999) - $202.8B ($389.42B adjusted for inflation)

As of March 2024, the acquisition that took place between the company known as Vodafone and the company known as Mannesmann in the year 2000 is still considered to be one of the biggest acquisitions that has ever taken place in the history of business and finance. The acquisition, worth $203 billion, saw Vodafone, a mobile service provider from the United Kingdom, acquiring a German-owned industrial conglomerate company known as Mannesmann.

This acquisition saw Vodafone emerge as the largest mobile service provider in the world and marked the beginning of dozens of acquisitions in the mobile telecommunications industry that followed in the coming years. This acquisition is still considered the biggest acquisition in the history of the world.

2. Shenhua Group and China Guodian Corporation (2017) - $278B ($361.17B adjusted for inflation)

The merger between Shenhua Group and China Guodian Corporation is considered to be the largest merger between two equals in the year 2017. The Shenhua Group is considered to be the largest coal supplier in China, and China Guodian Corporation ranks amongst the top five in the supply of electricity in China.

This merger deal, which amounts to $278 billion, has resulted in the largest power utility company in the world in terms of capacity. The rationale behind this merger deal was to achieve a balance between coal and renewable energy sources, as provided in the environmental and economic policies in China.

3. AOL and Time Warner (2000) - $182B ($340.16B adjusted for inflation)

As discussed in the introductory part of this article, big doesn’t always mean better, and the acquisition between AOL, a US-based Internet service provider, and Time Warner, a US-based cable television company, which took place in 2000, is a perfect example of this maxim.

This deal has now become a textbook example in less than three decades of how not to execute a mergers and acquisitions deal with all the hallmarks of overpaying, culture clash, and, in hindsight, two giant media companies that didn’t know where the media business was headed.

The value of this deal cratered when the dot-com bubble burst just two months after signing the deal, which was to be known as the largest merger in history, which ultimately collapsed in 2009, 9 years after signing the deal.

4. ChemChina and Sinochem (2018) - $245B ($311.84B adjusted for inflation)

ChemChina and Sinochem is another mega deal that’s part of the larger Chinese strategy of improving their competitive position on the world stage by reducing the overall number of state-owned enterprises within their country by merging their largest companies into one giant company.

This mega deal has led to the creation of the largest industrial chemicals company within the world, called Sinochem Holdings, which has now managed to surpass even their largest competitors within North America, such as the German behemoth known as BASF, in terms of size.

5. Gaz de France and Suez (2007) - $182B ($283.67B adjusted for inflation)

France has a love affair of sorts when it comes to the national champions of their country, the large French companies that compete on the world stage, proudly flying the French flag. It was thus only natural that in 2007, Nicholas Sarkozy, the President of France, stepped in to ensure that the deal went through.

Yes, you heard that right – the President of France acting as part-time investment banker! Suez is one of the ‘majors’ within the Oil & Gas Industry today, but the fact that the stock prices of the company did not move over the last one and a half decades says it all about what shareholders felt of the deal itself.

The merger, one of the biggest in the energy sector, has led to the formation of the fourth largest energy group in the world, as well as the second largest electricity and gas group in Europe. The companies that have merged have been able to form a diversified, flexible energy supply stream with a high-performance electricity production base.

6. Glaxo Wellcome and SmithKline Beecham merger (2000) - $107B  ($199.99B adjusted for inflation)

The merger of these two largest pharmaceutical companies in the UK has resulted in the formation of what is currently the 10th largest pharmaceutical company in the world, one of the two British companies in the top 10, the other being AstraZeneca, currently ranked 7th.

However, as has been seen with many of these mergers on this list, it hasn’t been well received by shareholders, currently trading 25% lower than it was at the time of the merger.

This, and many other bolt-on acquisitions in the consumer industry over the last decade or so, may be the reason for the company being split into two separate entities in the not-too-distant future.

7. Verizon and Vodafone (2013) - $130B ($178.11B adjusted for inflation)

Vodafone has been involved in so many mergers over the last two decades or so that perhaps by now they should be getting quite good at it!

The $130 billion merger allowed Verizon to pay for their division of wireless in the US. At the time of the merger, it was the third-largest merger in the history of mergers, the other two mergers being the ones that Vodafone were involved in. Verizon was looking for full control over their division of wireless, and this merger allowed them to get it.

It was the end of their often tumultuous relationship with Vodafone, which had been over a decade or so at this point. Verizon was looking to create new wireless networks that could compete with the ever-increasing competitive market that was in place at this time.

8. Dow Chemical and DuPont merger (2015) - $130B ($175.49B adjusted for inflation)

The merger between Dow Chemical and DuPont meant that when they announced their intention to merge, everyone knew because it meant that they would become the largest chemical company in terms of sales in the world. It also meant that they would stop competing with each other, making it a classic example of a horizontal merger.

Just after their merger was completed, in 2018, Dow Chemical and DuPont had just begun making a revenue of $86 billion every year. However, it wasn’t meant to be because in 2019, they announced that they would be spinning off into three different companies.

9. United Technologies and Raytheon (2019) - $121B ($151.66B adjusted for inflation)

The merger between United Technologies Corporation and Raytheon means that a new entity is emerging that will be a leader in the defense and aerospace sector.

However, having said that, since their merger was completed, Raytheon can use the expertise of United Technologies in terms of high-temperature materials for jet engines. Also, in terms of directed energy, United Technologies can use their technology in terms of power generation and management.

However, investors don’t appear to believe in this move, and the company’s shares have faced a decline of 25% just after the deal was completed.

10. AB InBev and SABMiller merger (2015) - $107B  ($144.44B adjusted for inflation)

If the stock price of the company after the deal has been completed is to be taken as a criterion of success, then the formation of AmBev after the merger of InBev and SABMiller in 2015 was a failure.

The rationale behind the merger was good, as it brought together two of the world's biggest breweries and united some of the world's favorite drinks under one roof.

However, they did have one major problem, which was that they didn’t foresee the craft beer phenomenon that would disrupt the industry in the way that it has. Having acquired quite a few craft breweries, it appears that they have finally got their act together.

11. AT&T and Time Warner (2018) - $108B ($137.47B adjusted for inflation)

The merger that AT&T and Time Warner attempted has not only been viewed with suspicion by the antitrust regulators but has also brought back memories of the last time that Time Warner was involved in a massive merger.

Having been given the best part of two decades to learn from their mistakes, and AT&T being a much larger cash generator than AOL, it appears that the merger has been much better thought out than the last one that involved Time Warner.

12. Heinz and Kraft merger (2015) - $100B  ($135B adjusted for inflation)

The merger that took place between Heinz and Kraft to form the Kraft Heinz company is just one of the many “megadeals” that has a negative impact on the stock price of the companies that have undergone the merger.

The reasons for this can be attributed to the fact that the companies that underwent the merger were accused of having poor accounting practices before the merger took place. Another reason has been the zero-based budgeting that has been a cost-cutting tool, which has been in place when the old brands had to be updated as opposed to the budgets being cut.

13. BMO Financial Group and Bank of the West (2021) - $105B ($126.64B adjusted for inflation)

BMO Financial Group, on December 20, 2021, announced that it has agreed to buy BNP Paribas SA’s unit Bank of the West and its subsidiaries, which have assets of $105 billion.

The merger that took place will definitely give a boost to the presence of BMO Financial in the United States. By acquiring Bank of the West, BMO Financial can increase its client base, enhance its presence in new markets, and also enhance its capabilities by utilizing the services of Bank of the West.

14. Bristol-Myers Squibb and Celgene merger (2019) - $95B  ($119.07B adjusted for inflation)

This is another “megadeal” that, in spite of its enormous size, has failed to attain the status of a “merger of equals,” and this has been evidenced in Celgene’s status as a subsidiary of Bristol-Myers Squibb.

This is a merger of two of the biggest producers of cancer medication in the world, and we hope this merger is worth so much more than the sum of its parts.

15. Pfizer and Warner-Lambert (2000) - $90.27B ($168.72B adjusted for inflation)

Pfizer acquired Warner-Lambert in the year 2000 in a merger deal worth more than $90 billion. This merger allowed the company to merge two of the fastest-growing entities in the industry. Therefore, the second-largest pharmaceutical company in the world was formed at that time, with revenues of more than $30 billion annually. 

This merger gave Pfizer the rights to Lipitor, which is a cholesterol drug and became the best-selling drug in the world in the year 2003, with revenues of more than $13 billion annually. This merger gave the company diversity in terms of the portfolio of the company, including Listerine mouthwash and Schick and Wilkinson Sword wet shave products.

16. Energy Transfer Equity and Energy Transfer Partners (2018) - $90B  ($114.55B adjusted for inflation)

The deal is part of the company’s plan to simplify the corporate structure of Energy Transfer Equity. The deal involves the conversion of each unit of ETP into 1.28 ETE units, which has changed the shareholding of the companies and allowed them to operate under a new name. 

The company, ETE, has been renamed Energy Transfer LP, which has been trading on the New York Stock Exchange under the ticker symbol "ET." The other company, ETP, has been renamed Energy Transfer Operating L.P.

17. AT&T and BellSouth merger (2006) - $86B ($136.83 adjusted for inflation)

The M&A deal between AT&T and BellSouth in 2006 for a consideration of $86 billion is one of the major deals in the telecommunications sector. The deal involved the merger of two important parts of the monopoly previously enjoyed by AT&T. The deal allowed AT&T to merge BellSouth’s wireline business with its operations.

The acquisition also allowed AT&T to gain full ownership of BellSouth’s stake in Cingular Wireless, which was then the largest mobile telephone service provider in the US. However, the Federal Communications Commission cleared the deal for AT&T after it agreed to uphold network neutrality and freeze some wholesale rates for competitors.

‍18. Unilever plc and Unilever N.V. (2020) - $81B  ($99.06B adjusted for inflation)

The M&A deal between Unilever plc and Unilever N.V. in 2020 was a unification strategy. The main objective was to develop a cohesive organization in which day-to-day activities could be streamlined and flexibility allowed.

As a result of the merger between Unilever plc and Unilever N.V., they wanted to ensure that nothing changed in their business activities, locations, or staffing levels in either The Netherlands or in the United Kingdom.

17. Walt Disney and 21st Century Fox (2017) - $52.4B ($68.08B adjusted for inflation)

The merger that took place between Walt Disney and 21st Century Fox in the year 2017 was an important event in the M&A history of the firms. The merger was for an aggregate consideration of $52.4 billion. The objective of the firm was to increase their presence globally. 

They also sought to increase the diversity of their content. They wanted to add more successful franchises to the ones they already had..

19. BHP Group Limited and BHP Group plc merger (2021) - $80.7B ($97.33B adjusted for inflation)

In the year 2021, the merger of BHP Group Limited and BHP Group plc was announced. This merger was for the unification of the corporate structure of BHP under the existing parent company, BHP Group Limited, which is based in Australia. The firm sought to position itself in such a way that it could grow in the future, especially in sectors such as electrification and decarbonization. 

In addition, the unification of the company gave BHP the opportunity to adapt, adjust, and manage the operations of the company, including the opportunity to make crucial decisions for the company, especially in the context of the ever-changing nature of the global economy. 

20. Exxon and Mobil merger (1999) - $80B ($153.62B adjusted for inflation)

The Exxon-Mobil merger of 1999 for $80 billion was an attempt by the company to merge two of the biggest offshoots of the original John D. Rockefeller oil monopoly that dominated 90% of the United States oil production until the year 1911 when the company was dissolved after the Supreme Court of the United States ruled in favor of the dissolution of the company.

The Exxon-Mobil merger gave birth to one of the biggest energy companies in the world. This move gave the company the opportunity to compete favorably in the global economy while at the same time maintaining the competitive advantage of the company in the industry.

21. Linde AG and Praxair merger (2018) - $80B ($101.83B adjusted for inflation)

In the year 2018, Linde AG and Praxair completed their merger to form the biggest industrial gas company in the world. The merger gave birth to one of the biggest companies in the industry with a capitalization of $90 billion and over 80,000 employees in more than 100 countries.

22. Royal Dutch Shell plc and Royal Dutch Shell N.V. merger (2021) - $71.5B ($86.24B adjusted for inflation)

Royal Dutch Shell announced that it would be merging its dual-class share structure into a single class of shares. The company has maintained a dual-class share structure since 2005. The company has been facing a lot of corporate governance issues because of its dual-class share structure. The company announced that it would be unifying its share class and changed its name to Shell plc.

23. CVS Health and Aetna merger (2018) - $70B ($89.1B adjusted for inflation)

The merger between CVS Health and Aetna has created a healthcare model that will integrate the healthcare services offered by CVS Health and the insurance services offered by Aetna. This merger has made healthcare more localized and made it more convenient for consumers to access healthcare services.

24. Saudi Aramco and SABIC (2019) - $69.1B ($86.61B adjusted for inflation)

Saudi Aramco has signed a deal to acquire 70% equity in Saudi Basic Industries Corporation, also known as SABIC, which is one of the largest petrochemical companies in the world. SABIC offers Saudi Aramco a wide range of products such as chemicals, fertilizers, and plastics, making it easier for it to compete in a global market that is growing every day.

25. AbbVie and Allergan plc (2019) - $63B ($78.96B adjusted for inflation)

The acquisition deal between AbbVie and Allergan plc in 2019 has helped AbbVie expand its business in key therapeutic areas through products such as Botox, Juvederm, and Vraylar. AbbVie avoided business risks through the acquisition of Allergan plc due to the introduction of similar products for its best-selling drug in the immunology business segment, Humira.

26. Walt Disney and 21st Century Fox (2017) - $52.4B ($68.08B adjusted for inflation)

In the year 2017, The Walt Disney Company acquired 21st Century Fox in December. The acquisition was done to increase their presence globally and add diversity to their content portfolio. 

‍27. Bayer and Monsanto (2018) - $63B ($80.19B adjusted for inflation)

The merger of Bayer and Monsanto, which cost the company $63 billion dollars, has resulted in the creation of one of the biggest agrochemical companies in the world. The acquisition of Monsanto by Bayer has helped the company to enhance its agricultural business segment by utilizing the expertise of Monsanto. This has enabled Bayer to emerge as the leader in the industry in the segment of seeds, traits, and agricultural chemicals.

However, the company has not been able to manage the integration of the acquired entity since the completion of the merger in the year 2018. The challenges faced by Bayer can be attributed to the challenges inherited from the acquisition of Monsanto.

28. Microsoft and Activision Blizzard (2023) - $75.4B ($79.51B adjusted for inflation)

Microsoft Corporation has announced on January 18, 2022, that they have planned to acquire Activision Blizzard for $68.7 billion. The primary reason for the strategic acquisition of Activision Blizzard by Microsoft Corporation was to enhance their gaming business segment to a significant extent. 

After facing many challenges from the regulatory authorities, the merger was completed on October 13, 2023. This has resulted in a cost of $75.4 billion to the company and has emerged as one of the biggest mergers in the gaming industry segment.

29. Broadcom and VMWare (2023) - $61B ($64.33B adjusted for inflation)

In the year 2023, Broadcom acquired VMWare with an aim to enhance their infrastructure software segment by leveraging the expertise of VMWare to deliver multi-cloud services.

The acquisition process has to go through a rigorous scrutiny and review process owing to the enormity of both businesses. This has resulted in involving various jurisdictions across the globe with an aim to assess the impact of the acquisition on competition in the technology industry.

30. Exxon Mobil and Pioneer Natural Resources (2023) - $59.5B ($62.75B adjusted for inflation)

In October 2023, Exxon Mobil and Pioneer Natural Resources agreed to a merger deal with an aim to reach a deal that would enable both companies to utilize their strengths in terms of total capacity in the energy sector. The acquisition deal was concluded in May 2024 to form an unconventional business with the largest high-return development potential in the Permian Basin. ExxonMobil and Pioneer Natural Resources have a combined 1.4 million net acres in the Delaware and Midland Basins with an estimated 16 billion barrels of oil equivalent resource, as per an ExxonMobil Press Release.

31. S&P Global and IHS Markit (2020) - $44B ($53.81B adjusted for inflation)

S&P Global has announced that it would merge with IHS Markit in an all-stock deal worth $44 billion in November 2020. Due to this merger deal, S&P Global would be able to acquire a data company that offers financial information to 50,000 clients worldwide. The company was expecting to generate $5 billion in free cash flow every year by 2023.

32. Discovery, Inc. and WarnerMedia (2022) - $43B ($48.25B adjusted for inflation)

Discovery Inc. and WarnerMedia announced on April 8, 2022, that they would merge to improve their media and entertainment business worldwide. Due to this merger deal, the company has become known as Warner Bros. Discovery, which has acquired many companies in the media industry, such as CNN, HBO, Discovery Channel, HBO Max, and Discovery+. Warner Bros. Discovery has been propelled to compete with other companies in the media conglomerate, such as Netflix and Disney+, which provide content on different categories.

33. Pfizer and Seagen (2023) - $43B ($45.35B adjusted for inflation)

Pfizer’s acquisition deal with Seagen, which took place in March 2023, is worth $43 billion, making it the largest merger deal in the biopharma sector since 2019. Seagen is known for being a biotech company that specializes in the production of ADCs and other innovative drugs for cancer treatment. Due to this acquisition deal, Pfizer has been propelled to compete with other companies in the cancer treatment industry.

34. Elon Musk and Twitter, Inc. (2022) - $44B (49.38B adjusted for inflation)

One of the biggest tech deals that have been talked about in recent years is the deal between Elon Musk and Twitter, in which Musk acquired Twitter for a whopping amount of $44 billion in 2022. Musk then rebranded Twitter as X in 2023 and reduced Twitter’s workforce considerably. Twitter is now rebranded as X and is a crucial tool for Musk’s AI startup, xAI, which has exponentially grown to a whopping $50 billion valuation in a very short period of time. 

35. Altimeter and Grab Holdings (2021) - $40B ($48.24B adjusted for inflation)

Altimeter's stock-for-stock merger with Grab has been identified as the biggest de-SPAC merger to date. It is indeed a whopping $40 billion merger. Altimeter has helped Grab go public, not through an IPO but by a reverse merger. The rationale behind doing a reverse merger is to allow Grab to gain a higher market share in Southeast Asia by providing them with additional capital to propel their growth so that they can compete with their major competitors, such as Gojek.

ng them with additional capital to propel their expansion and face their fierce competition, particularly Gojek.

It's a win-win move for Altimeter because the merger carved an opportunity for them to invest in a fast-growing tech company with a solid market presence in a rapidly developing region.

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Lessons from successful and failed mergers and acquisitions 

As mentioned earlier, whether it was a successful or unsuccessful merger or acquisition deal, it’s definite that there are lessons to be learned in the mergers and acquisitions industry. However, here are some of the best lessons that we would like to focus on and discuss.

Never underestimate the power of culture 

Culture has always been one of the most underrated factors in mergers and acquisitions in the past. All that has mattered in all mergers and acquisitions deals in the past has been money. However, today people have realized the importance of culture in mergers and acquisitions deals. For anyone still not convinced about the importance of culture in mergers and acquisitions deals, you can take the example of the merger between Daimler Benz Group and Chrysler Group that took place on May 7th 1998.

It should be noted that Daimler was extremely aggressive in integrating with Chrysler. However, Chrysler was not comfortable with being dictated to in any manner by Daimler. The two companies did not get along well and continued to operate separately. It was a disaster all around, and in the end, Daimler Benz was left with no other option but to sell Chrysler to a company called Cerberus Capital Management.

Don’t take due diligence for granted

It should be noted that M&A practitioners should never take due diligence for granted and should turn all possible stones during the deal-making process. One wrong move may lead to serious headaches that may even lead to the destruction of the company. HP is one company that learned this lesson the hard way when it acquired Autonomy back in 2011.

The idea was for the HP company, which was originally involved in the production of computers and printers, to become a software company that offered services. However, things began to go wrong after the sealing of the deal, as the company realized that Autonomy was falsifying financial reports by selling hardware at a loss but then booking it as software licensing revenue.

Plan for integration early

The biggest mistake that any M&A practitioner may make is the failure to plan for integration at an early stage of the M&A deal-making process. This is where the value lies. 

Let’s consider the merger that took place between Sprint and Nextel Communications. This merger took place way back in 2005. The merger involved the coming together of two legal entities that formed the third-largest telecommunications company at that time. The idea was for the two entities to gain access to each other’s customers and then sell other products to each other’s customers. 

However, owing to the fact that the company did not plan for integration, it wasn’t prepared for what was about to happen after the close. Apparently, the company’s network didn’t use the same technology, nor was there any overlap. Moreover, the company also lost a lot of market share owing to the different marketing strategies that they employed. This helped the competitors gain their customers who were not satisfied with the services offered by the company.

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Final thoughts

All in all, it’s hard to argue which merger or acquisition in the history of the US has been the most successful, because sometimes it takes years for the value and potential of a merger or acquisition to formulate.

However, it’s been observed that the best mergers and acquisitions (just like some that have yet to be made in terms of M&A deals) are those that take into consideration best practices in communication, strategic goal/deal thesis, and integration planning.

Technology and tools may also be used in making a deal successful.

The DealRoom M&A Platform has been developed to assist M&A teams in effectively managing complex M&A deals. The DealRoom M&A Platform is a unified platform that has been specifically designed to meet the requirements of M&A teams by providing a streamlined solution to effectively manage all aspects of M&A deals, including M&A pipeline management, the entire due diligence process, and post-merger integration.