Papers filed Friday in Superior Court show the pop stars "are restored to the status of single, unmarried persons."
Lachey, 32, and Simpson, 25, starred in the MTV reality show, "Newlyweds: Nick & Jessica." The singer-actress filed for divorce in December after three years of marriage.
Simpson starred last year as Daisy Duke in "The Dukes of Hazzard." In May, Lachey released his second solo CD, "What's Left of Me," in which he sings about the pain of the pair's breakup.