Oliver Platt (born January 12, 1960) is an American stage, film, and television actor.

Platt was born in Windsor, Ontario, Canada to American parents Sheila Maynard, a clinical social worker who worked in Islamabad, and Nicholas Platt, a career diplomat who served as U.S. ambassador to Pakistan, Zambia and the Philippines. His family moved back to the United States when Platt was three months old. He is a distant cousin of Diana, Princess of Wales through his great-great-grandmother, Frances Work. When asked about Diana, his second-cousin once removed, Platt said, "I never met her. It's a non-story. I'd love to tell you we were confidantes. The truth is I don't know much more about it than you do."

Much of Platt's childhood was spent in Asia, where he played soccer. His family made frequent trips back to Washington, D.C., where they held Redskins season tickets.Platt is also a fan of the Boston Red Sox. When he was nine years old, Platt and his family visited Kennedy Center in Washington, where he watched a performance that helped inspire his acting career. "One of the performances that really made me want to be an actor started out with this probably 20-minute rambling, drunken monologue by this bum. And it was a young Morgan Freeman. I'll never forget it. This guy was just so riveting. He stood there on stage alone before the curtain went up, and he held this audience utterly rapt. Including myself, obviously."