Paul Edward Valentine Giamatti ( JEE-ə-MAH-tee; born June 6, 1967) is an American actor and producer. Beginning as a varied character actor, his roles evolved into portraying everyman protagonists that balance sardonic humor and flawed humanity. Making his film debut in 1991, 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 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. He would go on to earn Academy Award nominations for Best Supporting Actor for his portrayal of Joe Gould in the sports drama Cinderella Man (2005), and Best Actor for playing a disgruntled teacher in the coming-of-age dramedy The Holdovers (2023). He has also acted in The Illusionist (2006), Fred Claus (2007), Barney's Version (2010), Win Win (2011), The Ides of March (2011), 12 Years a Slave (2013), Saving Mr. Banks (2013), Love & Mercy (2014), Straight Outta Compton (2015), Private Life (2018), and The Debut (2026). 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 villain in the Paramount+ series Star Trek: Starfleet Academy (2026–present). On stage, Giamatti made his Broadway debut portraying Ezra Chater in the Tom Stoppard play Arcadia (1995). He returned to Broadway acting 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), the later of which earned him a nomination for the Drama Desk Award for Outstanding Actor in a Play.