Miroslav Hajn (21 September 1894 in Žamberk, Austria-Hungary – 6 September 1963 in Prague, Czechoslovakia) was a chief designer at ČKD-Praga,[1] one of the largest engineering companies in the former Czechoslovakia and today's Czech Republic.

[2] Hajn was first a founder and chief designer at Avia, along with Pavel Beneš, in 1919.

The two began repairing planes in a workshop within the complex of an old sugar factory in Prague.

From 1923 to 1925, the two developed the Avia BH-7, BH-9, and BH-11 monoplanes, launching the era of biplane fighters.

Three years later, their Avia BH-21 fighter was considered one of the world's best planes.