Marvin the Martian (or Marvin Martian) is a fictional character appearing in the Looney Tunes cartoons. Marvin's likeness appears in miniature on both the Spirit and Opportunity rovers on Mars.Marvin hails from the planet Mars, but is often found elsewhere. He is often accompanied by his dog "K-9," and sometimes by other creatures (one gag, first used in Hare-Way to the Stars (1957), being candy-sized "Instant Martians" that become full-size on addition of drops of water).

Marvin wears a Roman soldier's uniform (a reference to Mars being the Roman god of war) with old-fashioned basketball shoes. His head is a black sphere with only eyes for features. The crest of his helmet appears, with the "push broom" like upper section, to "comically" resemble an ancient Greek Hoplite's helmet. The appearance of the combination of Marvin's head and helmet allegedly led to Bugs Bunny thinking he was a "bowling ball wearing a spittoon" in one Looney Tunes animated short. Marvin is given a timid, nasal voice. The helmet and skirt that surround him are green and his skin is red to represent his Martian race or color. He is also known for his trademark quotes "Where is the kaboom? There was supposed to be an earth-shattering kaboom!" and "This makes me so angry, very angry indeed."

Marvin was casted as the referee in Space Jam, and then later had a major villainous role in Looney Tunes: Back in Action where he was hired by the ACME chairman, Mr. Chairman (Steve Martin), to finish DJ (Brendan Fraser) and the gang at Area 52. In the film's climax, he reappears to bring the Blue Monkey diamond to the ACME satellite, but is foiled by Bugs (who he duels in a parody of Obi Wan Kenobi and Jango Fett in Star Wars Episode II: Attack of the Clones) and Daffy (who arrives as Duck Dodgers to save Bugs after he is exhausted from the battle).

Marvin appeared in the Looney Tunes version of A Christmas Carol, Bah, Humduck! A Looney Tunes Christmas. He played as an employee at Daffy Duck's "Lucky Duck Super Store". Marvin was homesick for his planet, Mars, and wanted to go back for Christmas. However, Daffy would not let him take Christmas off, and demanded he and the other Lucky Duck employees work on Christmas Day. After being visited by the Christmas ghosts, Daffy changes his ways, and gives Marvin a rocket that will go faster than the speed of light, allowing him to make it to Mars by yesterday.

In nearly all of his appearances, Marvin is shown using a small pistol that fires either bubbles of pliable plastic or energy beams. He is also apparently able to survive over centuries, since he mentions doing over a thousand years of research to create the Illudium Q-36 Space Modulator, and he is seen in Duck Dodgers in the 24½th Century.