Grand Daddy I.U. is an American emcee who was born in Queens, New York, active during the golden age of hip-hop. He states his nom de plume is similar to the pronunciation of his first name, "Ayyub" (ah-yoob).

Grand Daddy I.U. was raised in Hempstead, Long Island, and was encouraged to begin performing by his brother DJ Kay Cee. He recorded a demo tape and gave it to Biz Markie, who signed him to the label Cold Chillin' Records in 1989. In 1990 he released his debut, Smooth Assassin, which spawned his one and only hit "Something New" (which sampled James & Bobby Purify's only hit—their signature tune "I'm Your Puppet)." He became noted for his high-end sartorial choices, always appearing in public wearing a suit and tie.