The R66 is a provincial route in KwaZulu-Natal, South Africa that connects Gingindlovu with Pongola via Eshowe, Melmoth and Ulundi.

It begins by going southwards for 19 kilometres, crossing the Pongola River, to reach a junction with the R69 route near a place named Magudu.

[1] The R66 continues southwards for 74 kilometres as the King Dinizulu Highway, crossing the Black Umfolozi River, passing through the city of Ulundi and crossing the White Umfolozi River, to reach a T-junction with the R34 route.

The R66 joins the R34 and they are one road southwards, heading for 22 kilometres to meet the eastern terminus of the R68 route just east of the Melmoth town centre.

[1] The R66 continues southwards for 43 kilometres, passing through Eshowe (east of the town centre), to reach a junction with the R102 route at Gingindlovu.