De La Soul Member Dave, AKA Trugoy the Dove, Dead at 54

David Jolicoeur -- also known as Dave and Trugoy the Dove, who was one of the three founding members of De La Soul -- has died.

Sources familiar with the situation tell TMZ the rapper passed away Sunday at a hospital in Maryland. No other details, including a potential cause, have been released ... but we're told his death appears to be from natural causes, and that he was battling an undisclosed illness.

De La Soul's official social accounts have yet to say anything about Dave -- ditto for the other two members and their own pages ... Kelvin Mercer (Posdnuos) and Vincent Mason (Maseo).

Dave was with DLS since the beginning, getting together in '87 and going on to crank out some of the most famous rap songs of all time. The group went on an incredible three-album run through the '90s -- with two of those being certified platinum and gold, respectively.

Some of their best-known tracks include ... "Me, Myself and I," "Eye Know," "The Magic Number," "Stakes Is High," "Ring Ring Ring," "Say No Go," "Breakadawn," "Oooh," "Buddy," "All Good," "Ghetto Thang," "I Am I Be," "Ego Trippin (Part 2)" and countless others.

De La Soul was unique in that they emerged in one decade, but seamlessly transitioned into another ... all while adapting their style and production to keep up with the times.

Three of their songs have been nominated for Grammys over the years, with one of those -- a smash hit collab with the Gorillaz in "Feel Good Inc." -- actually winning Best Pop Collaboration in 2006.

Their music has been hard to listen to in recent years ... for one reason or another, nobody has been able to stream their stuff on major platforms, but a deal was recently inked that'll finally allow their classic tunes to be played en masse starting next month.

Dave was 54.