The Hannover CL.II was an escort fighter, produced in Germany during World War I, designed in response to a 1917 requirement by the Idflieg for such a machine to protect reconnaissance aircraft over enemy territory.

The CL.II was a compact biplane of largely conventional configuration with single-bay staggered wings of unequal span.

The main units of the fixed tail skid undercarriage were linked by a cross-axle and the pilot and tail gunner sat in tandem, open cockpits, with the gunner's cockpit elevated above the line of the upper fuselage to afford him a greater field of fire.

The type was widely produced, and as the war continued, was increasingly employed as a ground attack machine, remaining in service in this role until the Armistice.

It however crashed during a public flight on August 23, 1919 in Warsaw, due to faulty bracing wires, killing its constructor Karol Słowik.