Z21

Z21 may refer to:


 * Flitzer Z-21 or Staaken Flitzer, a British amateur-built aircraft produced by Flitzer Sportplanes of Aberdare, Wales
 * German destroyer Z21 Wilhelm Heidkamp, Type 1936-class destroyer built for the Kriegsmarine in the late 1930s
 * New South Wales Z21 class locomotive (formally L.304 class), a class of steam locomotives built for the New South Wales Government Railways in Australia
 * The 2013 album #Z21 by Sweetbox, or the lead single from that album
 * Fleischmann/Roco Z21, a digital model railroad control system