Groot is a fictional character voiced by Vin Diesel and portrayed in various forms and capacities via motion capture by Diesel, Krystian Godlewski, Sean Gunn, James Gunn and Terry Notary, in the Marvel Cinematic Universe (MCU) media franchise, based on the Marvel Comics character of the same name. A tree-like extraterrestrial humanoid known as a flora colossus, the character is a member of the Guardians of the Galaxy and a close associate of Rocket in particular. The initial incarnation of the character sacrifices himself to save his allies during the battle against Ronan the Accuser at the climax of the first film, leaving behind a sapling which grows into a new Groot, colloquially known as "Baby Groot" and differentiated offscreen by James Gunn as the original's "son". Raised by Rocket as an adoptive son, the new Groot gradually grows to a similar size as his predecessor over the course of his next several appearances. He participates in the conflicts against Ego and then Thanos, falling victim to the Blip before being resurrected five years later by the Avengers and participating in the final battle against Thanos before departing for space with the Guardians. After the Guardians defeat the High Evolutionary, Groot continues to serve on the team, now under the command of Rocket.

Mark Sinclair, known professionally as Vin Diesel, is an American actor and film producer. One of the world's highest-grossing actors, he is best known for portraying Dominic Toretto in the Fast & Furious franchise.