The Daimler L21 or Daimler-Klemm L21 was a light twin engined, single seat, parasol winged sports aircraft built in Germany.

The wing was plywood covered from the forward spar to the leading edge, forming a torsion resisting box, and had internal wire bracing.

Both before and after the wing extension lift struts ran from the lower fuselage longerons to the end of the centre section, taking them well outside the engines on the final version.

[4][5] The L21 originally had a fixed undercarriage with solid plywood wheel without tyres, like those on the L15, mounted on an axle which passed through the fuselage on rubber blocks.

To absorb vibrations when the engines were at full power for take-off, these wheels were then fitted with tyres but the final undercarriage arrangement had rubber tyred, spoked wheels on a single, faired, rubber sprung axle held below the fuselage by a pair of very short V struts to the lower longerons on each side.

[6] The fuselage of the winner, D-623 hung in Klemm's factory at Böblingen Airport until destroyed by bombing in World War II.