T21 may refer to:
Aircraft Junkers T.21, a German reconnaissance aircraft produced in the Soviet Union Slingsby T.21, a British training glider
Rail and transit Minami-morimachi Station, in Kita-ku, Osaka, Japan Myōden Station, in Ichikawa, Chiba, Japan SJ T21, a Swedish locomotive Yakuriguchi Station, in Takamatsu, Kagawa Prefecture, Japan
Ships and boats , a tank landing ship of the Venezuelan Navy
Mistral T-21, a Canadian sailboat
Other uses T21 (rocket), an American chemical warfare rocket Down syndrome, or trisomy 21 Estonian national road 21 T21 road (Tanzania) T21 Light Tank, an American light tank
ThinkPad T21, a notebook computer Trisomie 21, a French cold wave group