The De Tomaso 505-38 is a Formula One racing car model, designed by Gian Paolo Dallara for manufacturer De Tomaso and raced during the 1970 Formula One season by Frank Williams Racing Cars.

The car was uncompetitive on debut, failing to finish or be classified the first four races of the year. Disaster struck at the following Dutch Grand Prix. Driver Piers Courage was killed in an accident that saw his De Tomaso 505 flip and catch fire. The loss deeply upset Williams; the distance the team principal now places between himself and his drivers has been attributed to this event.

Chassis: 505-38-1
Chassis 505-381 was the first of three chassis built by Dallara for DeTomaso. Piers Courage used the car in South Africa where he struggled at the back of the pack until a crash ended his race prematurely. At the subsequent Spanish Grand Prix, Courage was a little quicker but he destroyed his car during qualifying. The damaged tub was sent back to DeTomaso where it remained for three decades. It was eventually retrieved by Rick and Rob Hall.