Paul Edward Valentine Giamatti ( JEE-ə-MAH-tee; born June 6, 1967) is an American actor. Giamatti's breakout film role was in Private Parts (1997), followed by supporting roles in Saving Private Ryan (1998), Man on the Moon (1999), Big Momma's House (2000), Storytelling (2001), and Planet of the Apes (2001). He won wide acclaim for his lead roles in American Splendor (2003) and Sideways (2004), earning numerous accolades for both, including winning a Golden Globe Award for the latter. Giammati would go on to earn Academy Award nominations for Best Supporting Actor for his portrayal of Joe Gould in Cinderella Man (2005), and Best Actor for playing a disgruntled teacher in The Holdovers (2023). He has also acted in The Illusionist (2006), Shoot 'Em Up (2007), Fred Claus (2007), Barney's Version (2010), Win Win (2011), The Ides of March (2011), Cosmopolis (2012), 12 Years a Slave (2013), Saving Mr. Banks (2013), Love & Mercy (2014), Straight Outta Compton (2015), and Private Life (2018). On television, Giamatti played the title role in the HBO miniseries John Adams (2008), which earned him acclaim and several awards including a Primetime Emmy and Golden Globe. He starred as U.S. Attorney Chuck Rhoades Jr. in the Showtime series Billions (2016–2023), and 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). He also played Nus Braka, a part-Klingon, part-Tellarite villain in the Paramount+ series Star Trek: Starfleet Academy (2026–present). His notable theatre work include his Broadway debut portraying Ezra Chater in the Tom Stoppard play Arcadia (1995), Rev. Donald "Streaky" Bacon in the David Hare play Racing Demon (1995), and revivals of Anton Chekhov's Three Sisters (1997) and Eugene O'Neill's The Iceman Cometh (1999).