"I Will Possess Your Heart" is an alternative rock song recorded by the American band Death Cab for Cutie. The song depicts a one-sided obsessive relationship, which led Paste to name it one of the 25 creepiest songs about love. It is notable for its five-minute instrumental introduction as well as its music video which required location shooting across four continents. The song was the lead single from their sixth studio album, Narrow Stairs (2008).

The music is dominated by a repetitive bass guitar riff interspersed with piano chords and Ben Gibbard's vocals. It was released on March 18, 2008 in two versions: a full eight-minute album version, and a four-minute radio edit that omitted most of the instrumental introduction. The song was critically acclaimed and nominated for the 2009 Grammy Award for Best Rock Song.

The music video, released on April 11, 2008, features scenes of a young woman traveling alone to various places around the world, interspersed with the band performing in an industrial freezer room. The shoot involved the actress, director, and a crew of two traveling 27,977 miles in 13 days, and was shot on consumer-grade camcorders to achieve a sense of total realism and so that the film crew would blend in as tourists. The video won the 2008 MTV Video Music Award for Best Editing and was nominated for the Best Cinematography award.

The song's lyrics depict a one-sided obsessive relationship from the point of view of the pursuer, who implores the object of his affection that she needs to "spend some time" with him so that he might "possess [her] heart." Songwriter and lead vocalist Ben Gibbard noted that, although fictional, the song was inspired by the experiences of some of his friends. He added:

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