August Haefeli (Häfeli) (29 January 1887 – 5 June 1960) was a Swiss aircraft designer.
Under his direction, 185 aircraft were built, and some were flown by such notable airmen as Walter Mittelholzer, Oskar Bider, Robert Ackermann, and Max Cartier.
After moving to Mümliswil-Ramiswil, he attended school in Balsthal, where his father served as a clerk.
[4] From 1915 to 1929 he was chief designer and head of the aircraft construction department at the Eidgenoessische Konstruktionswerkstaette in Thun.
[7] A memorial stone for Haefeli was erected at the Balsthal baths in Switzerland on 7 June 2019.