Paul Edward Valentine Giamatti (/ˌdʒiːəˈmɑːti/JEE-ə-MAH-tee; born June 6, 1967) is an American actor. His accolades include a Primetime Emmy Award, three Golden Globes, and nominations for two Academy Awards and a British Academy Film Award.

After studying acting at the Yale School of Drama, he performed in numerous theatrical productions. Giamatti debuted on Broadway, portraying Ezra Chater in the Tom Stoppard play Arcadia (1995). Later that year, he played the Rev. Donald "Streaky" Bacon in the David Hare play Racing Demon (1995). He returned to theatre in the revivals of Anton Chekhov's Three Sisters (1997) and Eugene O'Neill's The Iceman Cometh (1999).

Giamatti's breakout film role was in Private Parts (1997), followed by roles in My Best Friend's Wedding (1997), Saving Private Ryan (1998), and Man on the Moon (1999). He won acclaim for his leading roles in American Splendor (2003), Sideways (2004), Win Win (2011), and Private Life (2018). He has also acted in Planet of the Apes (2001), The Illusionist (2006), Fred Claus (2007), The Ides of March (2011), 12 Years a Slave (2013), Saving Mr. Banks (2013), Love & Mercy (2014), and Straight Outta Compton (2015). He has earned Academy Award nominations for Best Supporting Actor for portraying Joe Gould in Cinderella Man (2005) and Best Actor for playing a disgruntled teacher in The Holdovers (2023).

On television, Giamatti played the role in the HBO miniseries John Adams (2008), earning him acclaim and several awards, including a Primetime Emmy and Golden Globe. He starred as U.S. Attorney Chuck Rhoades Jr. in the Showtime television series Billions (2016–2023). He earned Emmy nominations for his roles as Ben Bernanke in the HBO film Too Big to Fail (2011) and Harold Levinson in the ITV series Downton Abbey (2013). In the Netflix anthology series Black Mirror episode Eulogy (2025), he played a grieving lover.

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