Any aircraft capable of operating from the water, which uses its fuselage as a flotation device, as opposed to attached pontoons.

Technically, the first flying boat was the Curtiss D Flying Boat, which first flew in 1912. The Curtiss D class of aircraft also claimed the title of first airplane to fly to and from the deck of a ship, and the first aircraft to be hoisted aboard a ship. Despite these accomplishments, the D class of aircraft were primarily experimental.

The Curtiss E class is considered to be the first successful flying boat. First demonstrated in 1912 on Lake Keuka, at least one was delivered to the Navy as the C-1, and two were produced for the Signal Corps, the Army's first sea planes.