Johann Friedrich Klotzsch 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 as curator and director of the Royal Herbarium in Berlin.
The plant genus Klotzschia from the family Apiaceae and some plant species like Eugenia klotzschiana or Acianthera klotzschiana are named in his honour.