The 27-year-old singer dropped the upbeat song "Look What You Made Me Do" — which uses a sample from Right Said Fred's 1991 hit "I'm Too Sexy" — late Thursday to streaming platforms and iTunes.
The song, featuring elements of pop, dance and house, includes sharp lyrics like: "Honey, I rose up from the dead I do it all the time/I got a list of names and yours is in red, underlined I check it once/Then I check it twice."
The track ends with a voice message of Swift saying, "I'm sorry, but the old Taylor can't come to the phone right now. Why? Oh, 'cause she's dead."
Swift announced Wednesday that a new song would come this week followed by an album three months later.
"Reputation" is the follow-up to 2014's "1989," Swift's first official pop album after years of dominating in country music. "1989" launched seven hit singles, from "Shake It Off" to "Bad Blood," and won three Grammys, including album of the year.