Thomasina Winifred Montgomery (April 29, 1945 – March 16, 1970), professionally known as Tammi Terrell, was an American singer-songwriter, widely known as a star singer for Motown Records during the 1960s, notably for a series of duets with singer Marvin Gaye.

Terrell began her career as a teenager, first recording for Scepter/Wand Records, before spending nearly nine months as a member of James Brown's Revue, recording for Brown's Try Me label. After attending college, Terrell recorded briefly for Checker Records before signing with Motown in 1965. With Gaye, she scored seven Top 40 singles on the Billboard Hot 100, including "Ain't No Mountain High Enough", which was inducted into the Grammy Hall of Fame in 1999, "Ain't Nothing Like the Real Thing" and "You're All I Need to Get By".

Terrell's career was interrupted when she collapsed into Gaye's arms as the two performed at a concert at Hampden–Sydney College on October 14, 1967. Terrell was later diagnosed with a brain tumor and had eight unsuccessful surgeries before dying on March 16, 1970, at the age of 24.