from www.tmz.com – Ron Jeremy is in critical condition at an L.A. hospital … and is being treated for an aneurysm that was located near his heart … TMZ has learned.

Ron’s manager, Mike Esterman, tells TMZ … 59-year-old Ron drove himself to Cedars-Sinai hospital Tuesday afternoon after experiencing severe chest pain. Docs examined the legendary porn star … and discovered the aneurysm.

According to Esterman, Ron’s condition has worsened and he was transferred to the ICU. He’s currently being prepped for surgery.

Ron — and his 9-inch penis — have appeared in more than 2,000 X-rated movies together … including, “Super Hornio Brothers,” “High Heels, Low Standards,” and “A Christmas Orgy.”

He also spoofed Harvey Levin in the XXX spoof, “TMSleaze.”

Story developing …