In what decade is most of X-Men: First Class set?

Most of X-Men: First Class is set in the 1960s.

The 2011 film follows the young Charles Xavier and Erik Lehnsherr before they become Professor X and Magneto. Its main story takes place during the Cold War and builds toward the Cuban Missile Crisis in October 1962, when the developing relationship between the two mutant leaders reaches a breaking point.

The movie uses real historical events as the framework for its superhero story. Xavier and Lehnsherr become involved with the CIA, while the mutant villain Sebastian Shaw seeks to provoke a nuclear confrontation between the United States and the Soviet Union.

The film also includes a brief earlier historical sequence connected to Erik’s childhood during World War II. That prologue is set before the main narrative, so the movie is primarily associated with the 1960s rather than the 1940s. Its period setting distinguishes it from later X-Men films set in subsequent decades.