The 1981 Hang Ten 400 was an endurance race for Group C Touring Cars. The event, Round 3 of the 1981 Australian Endurance Championship, was staged on 13 September over 119 laps of the 3.1 km Sandown Park circuit in Victoria, Australia. The field was divided into four engine capacity classes:
Of the 55 cars which started the event, 26 were classified as finishers.
Peter Brock drove his Marlboro Holden Dealer Team VC Commodore to his record 6th consecutive Sandown endurance win, and his 7th victory overall. Reigning ATCC champion Dick Johnson finished 2nd after starting from pole in his Tru-Blu Ford XD Falcon after two spins thanks to an experiment with Shock absorber gone wrong. Third over the line was the Roadways Gown Hindhaugh VC Commodore of Steven Harrington and Garth Wigston.
Colin Bond and Steve Masterton were the winners of Class B in their Ford Capri, while Sydney's Peter Williamson was the winner of Class C Toyota Celica. The winners of Class D were Craig Bradtke and Rod Stevens driving a Mitsubishi Lancer.