Digital Underground Rap Star Cleetis Mack Dead

Digital Underground member Cleetis Mack has died, TMZ has learned.

A rep for the alternative hip-hop group known for kicking off Tupac Shakur's career tells us Mack passed suddenly ... adding his death "leaves a void in our Digital Underground family and in our hearts that can never truly be filled." A cause of death has not been revealed ... his age at the time of his death is unclear.

Mack -- who was known as "Clee" -- joined the group in 1993, six years after it was founded in Oakland, California by Shock G (Gregory Jacobs), Chopmaster J (Jimi Dright), and Kenny-K (Kenneth Waters). His first single with Digital Underground was "Wussup Wit the Luv" ... featuring Tupac.

Digital Underground tells TMZ ... Mack was "more than a part of the movement -- he was part of the soul behind it, bringing warmth, loyalty, and quiet strength to everyone around him. He will always be remembered by his humility, love, and spirited energy, qualities that lifted those around him and made a lasting impression on all who knew him."

Founding member Shock G died suddenly in April 2021.

Mack was one of dozens of members who joined the ever-evolving band over the years. They were known for their Top 10 hit "The Humpty Dance" ... and "Same Song," Tupac's recording debut.