Thanos is a fictional character from the Marvel Comics universe, created by writer Jim Starlin. He first appeared in "The Invincible Iron Man" #55 in 1973. Thanos is a powerful alien warlord from the planet Titan and is known for his immense strength, intelligence, and mastery of various cosmic powers. He is often depicted as a villain, seeking to obtain the Infinity Stones to achieve his goal of universal balance. In the Marvel Cinematic Universe (MCU), Thanos is portrayed by actor Josh Brolin. He serves as the primary antagonist in films like "Avengers: Infinity War" and "Avengers: Endgame." Thanos believes that by eliminating half of all life in the universe, he can create a better world. His quest for the Infinity Stones drives the plot of these films, showcasing his complex motivations and formidable abilities.