'Quantum Leap' Star Dean Stockwell Dead at 85

Dean Stockwell, who starred alongside Scott Bakula in "Quantum Leap," has died ... TMZ has learned.

The longtime actor -- his Hollywood career spanned 70 years -- died early Sunday morning at home, peacefully and of natural causes ... according to a rep.

Dean's most famous for his role as Admiral Al Calavicci on 'Quantum' ... he starred in all 97 episodes of the hit sci-fi TV show from 1989 to 1993. The cult classic series earned Stockwell multiple Emmy nominations, and the 1990 Golden Globe for Best Supporting Actor.

Stockwell started out a child actor for MGM Studios back in the 1940s, starring in films like "Anchors Aweigh" and "Gentleman's Agreement" -- and he had a steady string of roles right into the 1980s, when he not only landed the 'Quantum' role ... but had major turns in movies.

Dean got a Best Supporting Actor Oscar nomination for 1988's "Married to the Mob," and also co-starred in big films like the original "Dune," "Blue Velvet" and "Paris, Texas."

He found even more TV popularity when he joined the "Battlestar Galactica" cast in 2006. Thanks to that role, and his 'Quantum' stardom, Dean became a fixture at sci-fi conventions all over the country.

Dean is survived by his wife, Joy Stockwell and their 2 children, Austin and Sophie.

He was 85 years old.