In the 2011 movie Thor, Laufey is the leader and king of the Frost Giants. He rules Jotunheim, the icy realm inhabited by the Frost Giants, and is portrayed as one of Asgard’s oldest enemies. The character is played by Colm Feore.
Thor’s opening sequence establishes the history between Laufey and Odin. Years before the main story, the Frost Giants invade Earth, and Odin defeats them, taking the Casket of Ancient Winters and rescuing the infant Loki. Laufey is later revealed to be Loki’s biological father, although Loki is raised in Asgard as Odin’s son.
Laufey’s role is central to Loki’s identity crisis. After learning his true heritage, Loki seeks out Laufey and secretly offers to help him enter Asgard and kill Odin. Loki ultimately murders Laufey himself, using the act to appear loyal to Asgard while advancing his own plans. A common mix-up is calling Laufey simply a Frost Giant; he is specifically the ruler of the Frost Giants in the film, while Jotunheim is their home world.