"Black Dog" is a song by British rock band Led Zeppelin, which was released as the lead-off track of their untitled fourth album in 1971.

The sounds at the beginning are those of Jimmy Page warming up his guitar. He called it "waking up the army of guitars."

Led Zeppelin bass player John Paul Jones got the idea for "Black Dog" after hearing Muddy Waters' experimental psychedelic-blues album, Electric Mud. He wanted to try "electric blues with a rolling bass part." The start-and-stop a capella verses were inspired by Fleetwood Mac's 1969 song, "Oh Well." John Bonham's drumming was patterned after the riffs on Little Richard's "Keep a Knockin'". Despite its seeming simplicity, the song features a complex, shifting time signature that the band has sometimes claimed was intended to thwart cover bands from playing the song.

The song's title came from a nameless black dog that wandered around the Headley Grange studios during recording. It actually has nothing to do with the song itself.