Bernhard Rensch (21 January 1900 – 4 April 1990) was a German evolutionary biologist and ornithologist who did field work in Indonesia and India.

Starting his scientific career with pro-Lamarckian views, he shifted to selectionism and became one of the architects of the modern synthesis in evolutionary biology, which he popularised in Germany.

Rensch was born in Thale and as a young boy, he took an interest in observing the natural world and discovered a talent for drawing and painting.

He served in the German army from 1917 to 1920 and began to observe natural phenomena while he was held prisoner in France.

His work in this area would influence Ernst Mayr, who was also an assistant at the museum from 1927 to 1930, and would contribute to the development of the modern evolutionary synthesis.

[4] In 1937 he was forced to leave the museum because he refused to join the Nazi party, and took a position at a zoological garden in Münster.

He introduced the concept of Artenkreis (which Mayr translated as a "superspecies" and defined as "a monophyletic group of closely related and largely or entirely allopatric species”).