Peter MacNicol (born April 10, 1954) is an American actor. He received a Theatre World Award for his 1981 Broadway debut in the play Crimes of the Heart. His film roles include Galen in Dragonslayer (1981), Stingo in Sophie's Choice (1982), Janosz Poha in Ghostbusters II (1989), camp organizer Gary Granger in Addams Family Values (1993), and David Langley in Bean (1997).

MacNicol won the Primetime Emmy Award for Outstanding Supporting Actor in a Comedy Series in 2001 for his role as the eccentric lawyer John Cage in the FOX comedy-drama Ally McBeal (1997–2002). He is also known for his television roles as attorney Alan Birch in the medical drama Chicago Hope (1994–98), X the Eliminator on Harvey Birdman: Attorney at Law (2000–2007), Tom Lennox in the sixth season of action-thriller 24 (2007), as physicist Dr. Larry Fleinhardt on the CBS crime drama Numbers (2005–10), Dr. Stark on Grey's Anatomy (2010–11), Jeff Kane on the political satire series Veep (2016–19), Doctor Octopus in The Spectacular Spider-Man, and Nigel the Advisor on Tangled: The Series.