His first canonical appearance in a Star Wars movie was in The Empire Strikes Back, in which his name is not actually heard in the dialogue. He is first seen as one of a group of bounty hunters hired by Darth Vader to track down Han Solo and the crew of the Millennium Falcon ("I want them alive. No disintegrations!"). He was the only hunter to figure out how the Falcon eluded Imperial pursuit and tracked the ship to Cloud City on Bespin, thus allowing Darth Vader to capture them. As partial payment, Vader allowed Boba Fett to take Han Solo, frozen in carbonite, back to Jabba to receive a bounty.
In Return of the Jedi, Boba Fett was at Jabba the Hutt's palace when Luke, Princess Leia, and Chewbacca rescued Han. He attempted to stop them, but Han activated Fett's jet pack, rocketing him into the Sarlacc which apparently ate him. However, non-canonical stories maintain that he escaped and is still active.
When the special edition of Star Wars was released in 1997, a scene with Boba Fett, Han Solo, and Jabba the Hutt was digitally inserted into the film before the Millennium Falcon took off from Mos Eisley.
Boba Fett is garbed in traditional Mandalorian armour with a string of Wookie pelts at his belt. His ship is called Slave I. In the movie Attack of the Clones it is revealed that he is the "unmodified" clone of the bounty hunter Jango Fett, whom he calls his father.