Blue Öyster Cult ( OY-stər; sometimes abbreviated BÖC or BOC) is an American hard rock band formed on Long Island in Stony Brook, New York, in 1967.

The band has sold 25 million records worldwide, including 7 million in the United States. The band's fusion of hard rock with psychedelia, and penchant for occult, fantastical and tongue-in-cheek lyrics, had a major influence on heavy metal music. They developed a cult following and, while achieving mainstream hits like "(Don't Fear) The Reaper" (1976) and "Burnin' for You" (1981), their commercial success was limited. Both songs, and others such as "Godzilla" (1977), remain classic rock radio staples. The band were early adopters of the music video format, and their videos received heavy rotation on MTV in its early period.

Blue Öyster Cult continued to make studio albums and tour throughout the 1980s, although their popularity had declined such that they were dropped from their longtime label CBS/Columbia Records, following the commercial failure of their eleventh studio album Imaginos (1988). Other than contributing to the soundtrack of the 1992 film Bad Channels and an album of re-recorded material, Cult Classic, in 1994, the band continued as a live act until releasing their first studio album of original material in ten years, Heaven Forbid (1998). The lackluster sales of Curse of the Hidden Mirror (2001) led to another hiatus from studio recording, but they continued performing live within the next decade-and-a-half. Two more studio albums were released in the 2020s, The Symbol Remains (2020) and Ghost Stories (2024), the latter of which is said to be the band's last.

Blue Öyster Cult's longest-lasting and the most commercially successful lineup included Donald "Buck Dharma" Roeser (lead guitar, vocals), Eric Bloom (lead vocals, "stun guitar", keyboards, synthesizer), Allen Lanier (keyboards, rhythm guitar), Joe Bouchard (bass, vocals, keyboards), and Albert Bouchard (drums, percussion, vocals, miscellaneous instruments). The band's current lineup still includes Bloom and Roeser, in addition to Danny Miranda (bass, backing vocals), Richie Castellano (keyboards, rhythm guitar, backing vocals), and Jules Radino (drums, percussion). The duo of the band's manager Sandy Pearlman and rock critic Richard Meltzer, who also met at Stony Brook University, played a key role in writing many of the band’s lyrics.