The Kiel FK 166 was a single-seat prototype "exercise" biplane built by Kiel Flugzeugbau in the 1930s.
The sole FK166 (registered D-ETON) was a biplane with cantilevered wings constructed mainly of wood with fabric and plywood covering. The elliptical plan upper wings, supported only by cabane struts in the centre, were given 2.5ð dihedral, spanning approx þ the span of the 0ð dihedral lower wing. Fitted with a fixed tail-wheel undercarriage the FK166 also featured a strut braced tailplane at the tip of the fin.