Johann Friedrich Klotzsch (9 June 1805, Wittenberg – 5 November 1860) was a German pharmacist and botanist.
His principal work was in the field of mycology, with the study and description of many species of mushroom.
Originally trained as a pharmacist, he later enrolled in pharmaceutical and botanical studies in Berlin. In 1830-32 he was curator of William Jackson Hooker's herbarium at Glasgow University. Beginning in 1834 he collected plants in Saxony, Bohemia, Austria, Styria and possibly Hungary. In 1838 he replaced Adelbert von Chamisso (1781-1838) as curator and director of the Royal Herbarium in Berlin.
The plant genus Klotzschia from the family Apiaceae is named in his honour.