Johann Jacob Paul Moldenhawer (11 February 1766 – 21 August 1827) was a German botanist who made a number of important discoveries in plant anatomy.
He was born in Hamburg, the son of a minister, and started out studying theology and the classics.
At some unknown point he became interested in plants, and in 1791 he published Tentamen in historiam plantarum Theophrasti, on Theophrastus, and the following year he is recorded as "Extraordinary Professor of Botany and Fruit Tree Culture" (außerordentlicher Professor für Botanik und Obstbau) at the University of Kiel.
Immediately subsequently he concentrated on fruit tree culture.
Moldenhawer's contributions center on the microscopic examination of plant tissues, for which he devised techniques to separate the cells from the middle lamella layer that separates them.