Sizaire-Naudin was a French automobile manufacturer.

Sizaire-Naudin began around 1905 with basic single cylinder vehicles. Independent front suspension by transverse leaf springs and sliding pillar identical to earlier Decauville motor vehicle.

Unique gear box by means of an integral 3 speed differential - 3 straight cut pinions brought to bear in turn on a single large straight cut crown wheel. Enjoyed great success in early voiturette races with rules which limited cylinder bore (but did not specify stroke length).

By 1911 the single cylinder format was outmoded, and an attempt to fit 4 cylinder engines did not result in significantly increased sales.