Adolf Otto Reinhold Windaus (December 25, 1876–June 9, 1959) was a German chemist who won a Nobel Prize in Chemistry in 1928 for his work on sterols and their relation to vitamins.

He started studying medicine and chemistry in Berlin and later in Freiburg. He got his PhD in early 1900. In 1913 he became professor for chemistry at the University of Innsbruck and in 1915 he changed to the University of Göttingen where he stayed until his retirement in 1944.