Emergency services were called to the crash on the narrow road leading up to the Loughbeg plant at approximately 7.20pm.
The motorcyclist, a man in his 40s, was pronounced dead at the scene while the driver of the car was uninjured.
The road was closed to the public for a technical examination into the night and workers at the plant were asked to remain onsite to facilitate garda crash examinations.
Two units of the fire service, from Carrigaline and Crosshaven, responded to the incident along with three ambulances and gardaí.
Local senator Tim Lombard said it was tragic to hear of another fatality on Irish roads.
“I know the location well and the traffic in Ringaskiddy is enormous, but to hear of a fatality in the area is very sad,” he said.
Tonight’s incident follows a tragic bank holiday weekend on Irish roads when five people lost their lives, bringing the number of fatalities so far this year to 39 — a rise of 30% on last year. The area around Ringaskiddy employs more than 5,000 people in the pharma sector.
Gardaí have appealed for witnesses to contact Togher Garda Station on 021 4947120.