A man has been critically injured after a motorbike crash in the Waikato this afternoon.

The crash occurred on State Highway 1, near Fisher Rd, just north of Huntly about 2pm, police said in a statement.

No other vehicles were involved in the crash. The injured man has been airlifted to Waikato Hospital with critical injuries.

SH1 has been closed with south-bound traffic being diverted down Tahuna Rd and north-bound down Ohinewai South Rd.