A motorcyclist has died after a collision with a car in the Waikato.

The crash took place at 3.45pm today about 15km from Kopu on State Highway 25A, the Kopu-Hikuai Rd in the Thames-Coromandel District.

The highway remains closed as police and serious crash investigators work at the scene.

Motorists can expect delays and police thanked them for their patience, while advising those yet to travel to use alternate routes or delay their trip.