Rodney Muñoz -- a longtime Hollywood costume designer known for his work on "Jimmy Kimmel Live!" -- is dead.

Jimmy Kimmel announced Rodney's death Friday in a social media post ... calling him a "dear friend."

The cause and manner of death are unclear.

Jimmy says ... "Rodney was one of the most talented people I've had the pleasure of knowing. He was a funny, surly, hard-working man whose tough exterior hid a huge and generous heart."

He adds ... "Rodney helped many of us through difficult times. He was a devoted son, brother, and Uncle; a great baker, and a caring friend. No man saw me in my underpants more. We will miss Rodney as he joins his beloved parents in whatever comes next."

Rodney worked at ABC Studios as a costume designer for nearly 24 years ... before that, he designed costumes for David Letterman's late-night talk show on CBS.

He styled Jimmy for The Oscars and worked as a wardrobe stylist on "Fear Factor."

Rodney was 60.

RIP