The Curtiss O-40 Raven was an American observation aircraft of the 1930s which was built and used in small numbers.

In 1931, in response to a United States Army Air Corps requirement for a new observation aircraft, Curtiss designed the Model 62, a single-engined biplane with the lower wing much smaller than the upper, known as a sesquiplane (i.e. "one-and-a-half wings"), while the outer panels of the upper wings were swept back to avoid centre-of-gravity problems.

A further four YO-40As were ordered, but they were redesigned as monoplanes by removing the lower wing, the resultant aircraft being designated Y1O-40B.

[2][4] The four Y1O-40Bs were delivered in June 1933, and after service tests, were redesignated O-40B,[5] being operated by the 1st Observation Squadron of the USAAC.

[6] While the aircraft's performance and manoeuvrability were good, the Air Corps was disappointed with the cockpit arrangements and the low fuel capacity,[2] and no more orders followed.