Wallace Michael Shawn (born November 12, 1943) is an American actor, essayist, playwright, and screenwriter. He is known for playing Vizzini in The Princess Bride (1987), Mr. Hall in Clueless (1995), Dr. John Sturgis in Young Sheldon (2017–2024), and voicing Rex in the Toy Story franchise (1995–present).

Shawn also appeared in The Bostonians (1984), Prick Up Your Ears (1987), Scenes from the Class Struggle in Beverly Hills (1989), Vanya on 42nd Street (1994), My Favorite Martian (1999), The Double (2013), Maggie's Plan (2015), and Marriage Story (2019). He appeared in six Woody Allen films including Manhattan (1979), Radio Days (1987), and Rifkin's Festival (2020). His television work includes recurring roles as Jeff Engels in The Cosby Show (1987–1991), Grand Nagus Zek in Star Trek: Deep Space Nine (1993–1999), Cyrus Rose in Gossip Girl (2008–2012), and Father Frank Ignatius in Evil (2022–2024).