The Groundlings is an American improvisational and sketch comedy troupe and school based in Los Angeles. The troupe was formed by Gary Austin in 1974 and uses an improv format influenced by Viola Spolin, whose improvisational theater techniques were taught by Del Close and other members of the Second City, located in Chicago and later St. Louis. They used these techniques to produce sketches and improvised scenes. Its name is taken from Shakespeare's Hamlet, Act III, Scene II: "...to split the ears of the groundlings, who for the most part are capable of nothing but inexplicable dumbshows and noise." In 1975 the troupe purchased and moved into its current location on Melrose Avenue.

The Groundlings School holds new sessions every six weeks with over 300 students per session, with more than 2,000 students per year going through the program. The competitive program with admission by audition, consists of five levels (Basic, Intermediate, Advanced Improv, Writing Lab, and Advanced Lab). Participants must satisfy instructors' requirements in order to advance.

The program takes years to complete, as 18-month to two-year wait-lists between upper levels are common. Students may be asked to repeat Basic and Intermediate classes multiple times. By the late 2000s, students had only one chance to complete classes in Improv and Writing. Failure to pass either of these classes means a student cannot complete the program, nor be invited into the Sunday Company.

Students may be voted into the Sunday Company, where they may remain for no more than two years. Many move on sooner than that. Many Groundlings performers have found success in movies and television, including several who have become cast members and writers on Saturday Night Live, MADtv, Reno 911!, and the network G4 while also being active on the internet, mainly YouTube.