"The Boy Is Mine" is a duet by American singers Brandy and Monica. It was written by LaShawn Daniels, Japhe Tejeda, Fred Jerkins III, Rodney "Darkchild" Jerkins, and Brandy, while production was helmed by Jerkins, Brandy, and Dallas Austin. It was released as the lead single from both singers' second albums from 1998, Never Say Never by Brandy and the album of the same name by Monica. Inspired by Michael Jackson and Paul McCartney's 1982 duet "The Girl Is Mine", the lyrics of the mid-tempo R&B track revolve around two women fighting over a man.

A duet is a musical composition for two performers in which the performers have equal importance to the piece, often a composition involving two singers or two pianists. It differs from a harmony, as the performers take turns performing a solo section rather than performing simultaneously. A piece performed by two pianists performing together on the same piano is a "piano duet" or "piano four hands". A piece for two pianists performing together on separate pianos is a "piano duo".