Jason Jordan Segel (/ˈsiːɡəl/; born January 18, 1980) is an American actor, screenwriter, producer, and author, best known for his role as Marshall Eriksen in the CBS sitcom How I Met Your Mother, as well as for his work with producer Judd Apatow on the television series Freaks and Geeks and Undeclared, and for the critically and commercially successful comedies he's starred in, written and produced.