The most-produced early Zero, with folding wingtips for carrier operations; treated here as the representative variant given its production volume and the classic Zero configuration it established.
After delivery of the first Model 11 aircraft, the production line introduced folding wingtips to fit carriers, resulting in the Model 21 — one of the most-produced early-war versions — which also gained a 520 L wing tank and a 320 L drop tank for extra range. By the time the lines switched to later models, Mitsubishi had completed 740 aircraft and Nakajima another 800. Two small-batch derivatives were built on this airframe: the Nakajima A6M2-N 'Rufe' floatplane and the two-seat A6M2-K trainer.