Which 1922 Lancia became the first production automobile with a monocoque chassis?

The 1922 Lancia Lambda became the first production automobile with a monocoque chassis.

Instead of using a separate body mounted on a conventional frame, the Lambda used its body shell as a structural part of the vehicle. This reduced weight and increased rigidity. Its design was the work of Vincenzo Lancia and engineer Battista Falchetto.

The Lambda also introduced independent front suspension, an important advance for ride comfort and handling. It was powered by a narrow-angle V4 engine, unusual at the time.

The Lambda is sometimes confused with the Citroën Traction Avant, which later made front-wheel drive and unitary construction famous. The Citroën was highly influential, but Lancia’s Lambda appeared earlier and is generally credited with pioneering production monocoque construction.