Gregory Everett Proops (born October 3, 1959) is an American actor, stand-up comedian and television host. He is widely known for his work on the British and American versions of Whose Line Is It Anyway?. He has also voiced the titular character on the American version of Bob the Builder: Project: Build It in series 10 to 14.

Proops was born in Phoenix, Arizona, and raised in San Carlos, California, a suburb south of San Francisco, attending San Carlos High School. He attended the College of San Mateo and spearheaded the comedy duo "Proops & Brakeman". Later, he took courses in improvisation and acting at San Francisco State University, though he never finished college.

After college, he joined an improv group with Mike McShane. Both Proops and McShane impressed producers Dan Patterson and Mark Leveson, who put them on their show, Whose Line Is It Anyway?. He frequently instigated jokes concerning various idiosyncrasies and differences between British English and American English, and would frequently banter with Clive Anderson on these matters (among others). He lived in London for four years when he was doing the show and lists McShane, Richard Vranch and Colin Mochrie among his best friends. After the show ended, he was recalled for the American version and has been a frequent "fourth contestant". Through 2020, he has appeared in 74 American Whose Line episodes, more than any other non-regular cast member.

Proops also appeared in every episode of the short-lived Drew Carey's Green Screen Show, where the performers would play improv games (some of which were taken from the show's main influence Whose Line Is It Anyway?) in front of a massive green screen. Later, animators would draw on the background and other props. In April 2011, Drew Carey's Improv-A-Ganza premiered on GSN featuring Proops along with other frequent guests from Whose Line is it Anyway? In July 2012, Proops appeared in ABC's improvisation show, Trust Us with Your Life.

In November 2011, Proops did a week on Royal Caribbean's Freedom of the Seas with the Lewis Black Comedy Cruise Tour. He performed the entire week of stand-up with other artists, which included a live, one-hour podcast in front of his entire audience.

Proops has performed his stand-up act across Britain, mainland Europe, Australia and New Zealand. His other credits include hosting Space Cadets, a mid-1990s science-fiction comedy game show on Channel 4 in the UK, which also featured Craig Charles (Dave Lister from Red Dwarf) and Bill Bailey, and appearances on BBC2's Mock the Week. He appeared as a panelist on the 2000 revival of To Tell the Truth. Proops has also hosted game shows, including VS. in 1999, Rendez-View in 2001, and Head Games, a Science Channel game show which ran for one season in 2009. Proops also competed on the November 8th, 1984 episode of Jeopardy!, losing to eventual five day champion John Genova. He would later record video clues for two Jeopardy! episodes in 2000 and 2001.

In addition to his stand-up and improv acts, Proops has done voice work in various films and TV shows, including Tim Burton's The Nightmare Before Christmas, and the miniseries Stripperella with Pamela Anderson. Proops provided the voice of Bob in the US version of the TV series Bob the Builder for the five seasons of Project Build It. He has also featured in 2003 film Brother Bear as the voice of one of the Love Bears and provided the voice as Cryptograf in 2006 film Asterix and the Vikings.

Proops has been involved with Turner Classic Movies since 2013, appearing on several of the network's podcasts and in person at public events. In 2016, he appeared as a television presenter for TCM, introducing comedy films by the Marx Brothers and Wheeler & Woolsey.