Karl Heider (28 April 1856, Vienna – 2 July 1935, Deutschfeistritz) was an Austrian zoologist and embryologist known for his research involving the developmental history of invertebrates.
He was the son of Moriz Heider, a pioneer of scientific dentistry in Austria.
In Vienna he was a student of zoologist Carl Claus and a colleague to Karl Grobben, with whom he formed a lifelong friendship.
In 1917 he was appointed to the chair of zoology at Friedrich Wilhelm University in Berlin.
[3] With German zoologist Eugen Korschelt, he was co-author of the classic "Lehrbuch der vergleichenden Entwicklungsgeschichte der wirbellosen Thiere", later translated into English and published as "Text-book of the embryology of invertebrates".