Michael Andrew "Duff" McKagan (born February 5, 1964) is an American musician. He was the bassist of the hard rock band Guns N' Roses for twelve years, achieving worldwide success in the late 1980s and early 1990s. McKagan rejoined the band in 2016, following their induction into the Rock and Roll Hall of Fame.

Toward the end of his first tenure with Guns N' Roses, McKagan released the solo album Believe in Me (1993) and formed the short-lived supergroup Neurotic Outsiders. After departing from Guns N' Roses in 1997, McKagan briefly reunited with his pre-success Seattle punk band 10 Minute Warning, and formed the still-active hard rock band Loaded, in which he performs lead vocals and rhythm guitar. Between 2002 and 2008, he played bass in the supergroup Velvet Revolver with his former Guns N' Roses bandmates Slash and Matt Sorum. He also performed with Alice in Chains in 2006, Jane's Addiction in 2010, and the supergroup Hollywood Vampires in 2016.

McKagan has collaborated in several short-lived projects with fellow Seattle-native musicians Mike McCready (primarily of Pearl Jam) and Barrett Martin (formerly of Screaming Trees), including Walking Papers and Levee Walkers.

In addition to his musical career, McKagan has established himself as a writer. He has written weekly columns on a wide variety of topics for SeattleWeekly.com, Playboy.com, and ESPN.com. Previously a high school dropout, he attended Seattle University's Albers School of Business and Economics in the early 2000s and founded the wealth management firm Meridian Rock.