"Back That Thang Up" (or the explicit version "Back That Azz Up") is a song recorded by American hip-hop artist Juvenile. It was released in February 1999 as the second single from his 1998 album 400 Degreez. The song, an explicit exploration of the same themes as Sir Mix-a-Lot's "Baby Got Back" was Juvenile's biggest hit single until the release of "Slow Motion" in 2004, peaking at number 19 on the Billboard Hot 100.