The Heinkel HD 26 was a reconnaissance seaplane developed in Germany during the 1920s for production in Japan.
It was intended as a smaller, single-seat counterpart to the HD 25, to provide a spotter aircraft for warships and to take off from a short ramp.
The HD 26 was a conventional biplane with staggered wings, twin float undercarriage, and an open cockpit.
The pattern aircraft supplied by Heinkel was powered by a 300 hp Hispano-Suiza V-8 engine, but the single example of the Aichi Navy Type 2 Single-seat Reconnaissance Seaplane built by Aichi had an Aichi-built 420 hp Bristol Jupiter VI instead.
Launching ramps were built on the battleship Nagato and the cruiser Furutaka for trials, but the HD 25 and HD 26 were already obsolete.