Ace Frehley, the original lead guitarist for KISS, is dead … TMZ has confirmed.

The legendary musician died Thursday after being hospitalized, and placed on life support … with the family coming to the difficult decision to turn off his ventilator.

We broke the story … Ace fell a couple weeks ago at his studio and suffered a blain breed … his health didn’t improve an he was put on a ventilator.

Ace was a founding member of KISS … joining forces with Gene Simmons, Paul Stanley and Peter Criss. He shredded guitar with the band from 1973 to 1982 … but he left the group amid substance abuse issues and creative differences.

He tried his hand at a solo career … founding the band Frehley’s Comet — a play on his ‘Spaceman’ nickname. The group played together from 1984 to 1988 then broke up … and Ace later rejoined the band for their 1996 reunion tour and remained with them until 2002.

Ace helped KISS create a ton of hits … including “Detroit Rock City,” “I Was Made for Lovin’ You,” and “Rock and Roll All Nite.”

His solo career might best be remembered for his covers of the songs “Back in the New York Groove” and “Into the Night.”

Ace was 74.

He’s the first original member of KISS to die.