What was the first car to use a unibody construction?

The Lancia Lambda was the first car to feature a load-bearing unitary body.

Introduced in 1922 and produced from 1922 to 1931, the Lambda was a major structural breakthrough. Instead of relying on a conventional separate chassis with the body mounted on top, its body structure carried much of the vehicle’s loads. Strictly speaking, the Lambda did not have a stressed roof, so historians and reference works often describe it as the first car with a load-bearing unitary body rather than an entirely modern unibody in every detail.

The Lambda’s innovation was not limited to construction. It used independent front suspension with sliding pillars and coil springs, an unusual arrangement for its era, along with a narrow-angle V4 engine and four-wheel brakes. These features helped make the car lighter, more rigid and more comfortable than many contemporaries.

The Citroën 2CV and Volkswagen Beetle came later and are sometimes mentioned in discussions of early unitary or semi-unitary construction. They did not precede the Lambda’s pioneering production design. Approximately 13,000 Lambdas were built across nine series.