Where is the thermostat located on a 1988 Buick Regal V6?

The thermostat on a 1988 Buick Regal V6 is located on the engine, at the bottom of the engine block, usually near the water pump. It's not easily accessible and typically requires removing some components to reach. You'll likely need a shop manual specific to your 1988 Buick Regal V6 for precise location and removal instructions. A picture of your engine bay would also be very helpful in identifying it if you're unsure.