Ron Jeremy is in critical condition at an L.A. hospital ... and is being treated for an aneurysm that was located near his heart!
Ron's manager, Mike Esterman, tells TMZ ... 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's worsened and he was transferred to the ICU. He's currently being prepped for surgery.
Porn On Bus: Employee Accidentally Shows X-Rated Movie To Patrons ( it wasn't FREE WILLY)!
Some riders on a Chilean inter-region bus on the Valparaiso line got a bit of a surprise when an employee apparently showed them a hardcore porn movie by accident.

