Robert Anthony Rist (born April 4, 1964) is an American actor. He is known for playing Cousin Oliver in The Brady Bunch, Martin in Grady and "Little John" in Big John, Little John. Rist is also known for voicing assorted characters in television shows, games and movies, most notably as the voice of Michelangelo in the films Teenage Mutant Ninja Turtles (1990), Teenage Mutant Ninja Turtles II: The Secret of the Ooze (1991), Teenage Mutant Ninja Turtles III (1993), and Casey Jones (2011); his other voice roles include Stuffy in Doc McStuffins, Whiz in Kidd Video, Star in Balto, Maroda in Final Fantasy X, and Choji Akimichi in Naruto. Additionally, he and director Anthony C. Ferrante provided music for the Sharknado film and the theme song for the Sharknado franchise. He played Ted and Georgette Baxter's adopted son David on The Mary Tyler Moore Show. He was also the voice of the stick man from the Handi Snacks commercials.

Rist was born in La Mirada, California on April 4, 1964.

As a child, Rist played Cousin Oliver in the final six episodes of The Brady Bunch. With the regular children all growing older, his inclusion was intended to reintroduce a cute, younger child to the series. However, the idea backfired as most viewers disliked the Oliver character and the plan became moot as ABC had opted to not renew the series even before his debut. This gave rise to the TV term "Cousin Oliver Syndrome".

After The Brady Bunch, he appeared as Glendon Farrell in Lucas Tanner starring David Hartman, "Little John" in the Saturday Morning series Big John, Little John, Tommy in the series premiere for the short-lived CBS drama series Bronk, and Martin in the short-lived Sanford and Son spin-off Grady. During 1975-77, Rist played David, son of Ted Baxter (Ted Knight) on The Mary Tyler Moore Show. He also appeared in three episodes of The Bionic Woman. In 1980, Rist played "Dr. Zee" in the first three episodes of Galactica 1980. He made four guest appearances on CHiPs and the short-lived CBS series Whiz Kids, and also played "Booger" in a failed Revenge of the Nerds TV pilot. In 1986, Rist had a supporting role as Milo in the action film, Iron Eagle, which was a box-office hit despite being critically panned.

As of 2006, Rist was acting, working with music and also working in film production. Rist produced a horror/comedy film, Stump The Band, directed by William Holmes and JoJo Hendrickson.

In 2013, he portrayed Robbie the Bus Driver in the camp horror film Sharknado. Rist said in an interview that his friend Anthony C. Ferrante came upon the film's poster at the American Film Market and became enthusiastic about the concept. When Ferrante said that he had been approached to direct the film, Rist insisted that Ferrante take the job, and that if he did, that he should have a part in it. He also mentioned that Sharknado was his very first red carpet premiere.

As an adult, Rist has worked as a voice actor, such as in the Teenage Mutant Ninja Turtles film series (as the voice of Michaelangelo); from 1984 to 1986, he starred in the Saturday morning cartoon Kidd Video, playing the character Whiz both in live-action music videos and animated sequences. He was the voice of Star, a mauve-and-cream Siberian Husky, in the animated 1995 Universal Studios film Balto, and to date, this is his first and only role in a full-length animated film. He was also the voice of Aaron in the PC game Star Warped. An episode of Batman: The Animated Series titled "Baby Doll" contained a character called Cousin Spunky that was intended to boost sagging ratings of the fictional sitcom Love That Baby, a clear reference to Cousin Oliver (Rist lent his voice to the episode, but did not play Cousin Spunky; his character was an adult).

Rist also voices characters Choji Akimichi from Naruto, and Bud Bison from Mega Man Star Force.