The BAT F.K.23 Bantam was a British single-seat fighter biplane produced by British Aerial Transport Company Limited of London during World War I. Frederick Koolhoven's first design for the British Aerial Transport Company (BAT) was the F.K.22 single-seat fighter.

The second machine was fitted with a 100 hp (75 kW) Gnome Monosoupape rotary engine and was the first to fly at Martlesham Heath in January 1918.

The production Bantam had to be modified due to unsatisfactory spin characteristics of the prototypes.

Continuous engine problems and downsizing of the Royal Air Force were factors in no more orders for the Bantam.

Koolhoven returned to Netherlands with one aircraft where it was re-engined with a 200 hp (149 kW) Armstrong Siddeley Lynx radial engine.