Underground is a 1968 album by Thelonious Monk. It features Monk on piano, Larry Gales on bass, Charlie Rouse on tenor sax, and Ben Riley on drums. Although this album is most widely known for its provocative cover image, which depicts Monk as a fictitious French Resistance fighter in the Second World War, it contains a number of new Monk compositions, some of which appear in recorded form only on this album. This is the last Monk album featuring the Thelonious Monk Quartet, and the last featuring Charlie Rouse (who appears on only half the tracks, having missed a recording session to attend his father's funeral).