Mary Wilson, the longest-reigning original Supreme, has died aged 76.
Wilson died on Monday night at her home in Las Vegas and the cause was not immediately clear, said publicist Jay Schwartz.
Wilson, Diana Ross and Florence Ballard made up the first successful configuration of The Supremes.
Ballard was replaced by Cindy Birdsong in 1967, and Wilson stayed with the group until it was officially disbanded by Motown in 1977.
The group's first number one, million-selling song, Where Did Our Love Go, was released on June 17 1964.
Touring at the time, Wilson said there was a moment when she realised they had a hit song.
"I remember that instead of going home on the bus, we flew," she told the Associated Press in 2014.
"That was our first plane ride. We flew home. We had really hit big."
It would be the first of five consecutive number ones, with Baby Love, Come See About Me, Stop! In The Name Of Love and Back In My Arms Again following in quick succession.
"I just woke up to this news," Ross tweeted, offering her condolences to Wilson's family. "I am reminded that each day is a gift," she added, writing: "I have so many wonderful memories of our time together."
The Supremes also recorded the hit songs You Can't Hurry Love, Up The Ladder To The Roof, and Love Child.
"I was extremely shocked and saddened to hear of the passing of a major member of the Motown family, Mary Wilson of the Supremes," said Motown founder Berry Gordy in a statement, according to Variety.
"The Supremes were always known as the 'sweethearts of Motown'."