But Pfizer's merger is just one of many eye-watering deals that have made 2015 the year of the mega-deal. In fact, five deals from 2015 make it in to the top 20 deals of all time.
In case you missed them, here are 2015's biggest deals, according to Dealogic data:
1. Pfizer and Allergan merge - worth $160bn
What happens when you mix Botox and Viagra? The largest ever pharma deal, and the second biggest merger in history, just behind Vodafone AirTouch's $172bn purchase of Mannesmann AG in 1999.
The long-awaited 'megabrew' merger between the world's two largest brewers held the top spot as biggest deal in 2015 for just two weeks before Pfizer's pharma extravaganza was announced.
3. Shell's takeover of BG group - worth $81.5bn
Investors are jittery thanks to oil's ongoing low prices, and competition concerns but if this oil merger goes ahead it will be number 11 on the leaderboard for all-time biggest deals, and create the largest company on the FTSE 100.
4. Charter and Time Warner join forces - worth $79.6bn
John Malone-backed cable group Charter will create America’s second largest cable and broadcasting company when it completes its deal to buy Time Warner.
The billionaire executive, who chairs Liberty Global, has also announced a (rather smaller) merger with Cable and Wireless, for just £3.5bn - bargain!
5. Dell's acquisition of EMC - worth $65.7bn
Michael Dell's purchase of data storage maker EMC, is the biggest tech deal ever (sensing a theme here...)
6. Heinz and Kraft merger - worth $62.6bn
7. Anthem takes over Cigna - worth $55.2bn
The deal, combining the second- and fifth-largest health insurers in the US, capitalises on the country's healthcare reforms as insurers, including Aetna and Humana, got caught up in a merger flurry.