Paul Dietrich Giseke (8 December 1741 Hamburg, Germany - 26 April 1796), was a German botanist, physician, teacher and librarian.
Giseke started his studies at the Academic Gymnasium in Hamburg. He joined the University of Göttingen in 1764 and graduated in 1767. He then went on an extended trip through France and Sweden and met Linnaeus, becoming his student and a lifelong friend - Linnaeus named the genus Gisekia after him.
Back from abroad he settled in Hamburg and started his practice as physician, but in December 1771 started teaching as Professor of Physics and Discourse at the Academic Gymnasium in Hamburg.