Ernst Johann Lemmermann (27 May 1867 in Bremen – 11 May 1915 in Bremen) was a German botanist who specialized in the field of phycology.
During his career he taught classes (Seminarlehrer) in Bremen, where he also worked as a botanical assistant at the Städtisches Museum für Natur-, Völker- und Handelskunde.
In Bremen he was an instructor to biologist Friedrich Hustedt (1886-1968), who named the diatom species- Achnanthes lemmermannii in honor of his former teacher.
Also, the blue-green algae species- Anabaena lemmermannii is named after Lemmermann.