Robert Clark Gregg Jr. (born April 2, 1962) is an American actor, director, and screenwriter. He is best known for playing Agent Phil Coulson in the Marvel Cinematic Universe films Iron Man (2008), Iron Man 2 (2010), Thor (2011), The Avengers (2012), Captain Marvel (2019), and the television spin-off series Agents of S.H.I.E.L.D. (2013–2020) and Disney series What If...? (2021). Gregg also voiced Phil Coulson on the animated series Ultimate Spider-Man (2012–2017) and in the video games Lego Marvel Super Heroes (2013), Marvel Heroes (2013), and Lego Marvel's Avengers (2016).

Gregg is also known for his role as FBI Special Agent Mike Casper on the NBC political drama series The West Wing (2001–2004) and as Richard, the ex-husband of Christine Campbell, in the CBS sitcom The New Adventures of Old Christine (2006–2010).

He wrote the horror film What Lies Beneath (2000), and wrote and directed the black comedy Choke (2008) and the comedy-drama Trust Me (2013). He appeared in the films The Adventures of Sebastian Cole (1998), One Hour Photo (2002), In Good Company (2004), When a Stranger Calls (2006), 500 Days of Summer (2009), Much Ado About Nothing (2012), The To Do List (2013), Labor Day (2013), and Live by Night (2016).