Donald Jay Fagen (born January 10, 1948) is an American singer-songwriter and musician who was the co-founder, lead singer, co-songwriter, and keyboardist of the rock band Steely Dan, formed in the early 1970s with musical partner Walter Becker. In addition to his work with Steely Dan, Fagen has released four solo albums, beginning with The Nightfly in 1982, which was nominated for seven Grammys.

In 2001, Fagen was inducted into the Rock and Roll Hall of Fame as a member of Steely Dan. Following Becker's death in 2017, Fagen initially wished to retire the Steely Dan name out of respect, but as of 2024 he continues to tour using the band name.