Chris Brown and Rihanna have reunited -- at least for a new song collaboration. The former couple, who called it quits in 2013 following a tumultuous relationship, including Brown's 2009 assault on the Barbadian singer, linked up to record "Counterfeit."

The song is included on Brown's new mixtape "Before the Party," which the singer dropped on Black Friday (Nov. 27) following news that his upcoming album "Royalty" was pushed back three weeks. The album was originally slated to drop Friday, but it will instead hit stories Dec. 18.

Of course, Brown and Rihanna's new song isn't the first time the pair has worked together on music. Rihanna appeared on Brown's song "Turn Up The Music," and he helped her remix her song "Birthday Cake."

The on-and-off couple also collaborated on "Bad Girl' and "Nobody's Business." In April, another duet called "Put It Up" leaked online. The track was supposed to be included on Brown's 2014 album "X," but it was yanked following their split.

Brown's "Before the Party" mixtape also includes songs with Fetty Wap, Wale, French Montana, Wiz Khalifa and Tyga.

Besides collaborating on songs with the 26-year-old singer, Rihanna is getting ready to release her studio album "Anti." The pop star has not announced an official release date, but Rihanna is slated to go on an Anti World Tour, beginning in February.

She announced last weekend that Travis Scott will be her opening act during the North American leg of her tour, and The Weeknd and Big Sean will accompany her while she tours in Europe.

Check out Brown and Rihanna's song "Counterfeit" HERE.