In the 2013 film 'Pacific Rim', what is the name of the first Jaeger ever built?

In the 'Pacific Rim' universe, the first Jaeger ever built is Brawler Yukon.

Brawler Yukon was the prototype for humanity's giant anti-Kaiju machines. It was developed after conventional weapons proved inadequate against the colossal monsters emerging from the Breach in the Pacific Ocean. The Jaeger program was conceived as a way to meet the Kaiju at their own scale without relying solely on nuclear attacks.

Brawler Yukon was a Mark-1 prototype, and its early testing exposed a major problem: a single pilot could not safely handle the enormous neural load created by the machine's control system. The solution was the Drift, a mental link that allows two pilots to share the Jaeger's movements and sensations. Brawler Yukon later entered combat and helped demonstrate that Jaegers could defeat Kaiju.

The common mix-up is selecting a famous machine from the film itself. Gipsy Danger, Crimson Typhoon, and Striker Eureka are later Jaegers; Brawler Yukon belongs to the franchise's early backstory and tie-in material, where the origins of the program are explored.