Who was the lead actor in Truman Capote movie?

There is no single movie called "Truman Capote". However, there are two prominent films about him:

* "Capote" (2005) starring Philip Seymour Hoffman as Truman Capote, which won him an Academy Award for Best Actor.

* "Infamous" (2006) starring Toby Jones as Truman Capote.

It's important to clarify which film you're referring to when asking about the lead actor.