The Martin KF-1 was an American biplane fighter aircraft designed and built by Captain James V. Martin.
The KF-1 started as a proposed "high-altitude fighter" designated the K.III. Powered by an ABC Gnat the K-3 first flew in May 1918, and was delivered to McCook Field the next month. The model was not ordered for production.
In 1921 Martin submitted an improved version with a larger engine and wider wings. The Navy ordered three, designated K-IV, then later KF-1. The version featured a central float and outriggers.