Steely Dan is an American rock band founded in 1971 in New York by Walter Becker (guitars, bass, backing vocals) and Donald Fagen (keyboards, lead vocals). Originally having a full band lineup, by the end of 1974 Becker and Fagen chose to stop playing live and continue Steely Dan as a studio-only duo, utilising a revolving cast of session musicians. Rolling Stone has called them "the perfect musical antiheroes for the seventies".

Becker and Fagen played together in a variety of bands from their time together studying at Bard College in Annandale-on-Hudson, New York. They later moved to Los Angeles, gathered a band of musicians and began recording albums. Their first, Can't Buy a Thrill (1972), established a template for their career, blending elements of rock, jazz, Latin music, R&B, blues and sophisticated studio production with cryptic and ironic lyrics. The band enjoyed critical and commercial success with seven studio albums, peaking with their top-selling album Aja, released in 1977.

After Steely Dan disbanded in 1981, Becker and Fagen worked sporadically on solo projects through the 1980s, although a cult following remained devoted to the group's work. Since reuniting in 1993, Steely Dan has toured steadily and released two albums of new material, the first of which, Two Against Nature, earned a Grammy Award for Album of the Year. Their final album of new studio material was 2003's Everything Must Go and the band has continued to release compilations, box sets and live albums on a regular basis. After Becker's death in 2017, Fagen reluctantly continued the group with himself as the sole official member.

They have sold more than 40 million albums worldwide and were inducted into the Rock and Roll Hall of Fame in March 2001. VH1 ranked Steely Dan at No. 82 on their list of the 100 Greatest Musical Artists of All Time. Rolling Stone ranked them No. 15 on its list of the 20 greatest duos of all time.