William Joseph 'Billy' Baldwin (born February 21, 1963) is an American actor, producer, and writer, known for his starring roles in such films as Flatliners (1990), Backdraft (1991), Sliver (1993), Fair Game (1995), Virus (1999), Double Bang (2001), as Johnny 13 in Danny Phantom (2004–2007), Art Heist (2004), The Squid and the Whale (2005), as Senator Patrick Darling on the ABC drama Dirty Sexy Money (2007–2009), Justice League: Crisis on Two Earths (2010), and was a regular guest on Gossip Girl as William van der Woodsen and Parenthood as Gordon Flint. He also starred as lead detective Brian Albert in the Lifetime Original Movie The Craigslist Killer.

He is brother to actors Alec Baldwin, Stephen Baldwin, and Daniel Baldwin. He is married to singer Chynna Phillips (Wilson Phillips) and they have 3 children.