Gerdt Hardorff (11 May 1769, Steinkirchen - 19 May 1864, Hamburg) was a German painter, art collector and drawing teacher.
From 1788 to 1794, thanks to a scholarship from that institution, he studied at the Dresden Academy of Fine Arts with the portrait painter, Giovanni Battista Casanova.
Within a short time, he received numerous commissions, both for portraits (including one of the famous poet, Friedrich Gottlieb Klopstock) and church decorations.
He became a citizen of Hamburg in 1797, and married his childhood sweetheart, Juliane Mielck, the daughter of a local merchant.
His students included Louis Asher, Günther Gensler, Georg Haeselich, Hermann Kauffmann, Henri Lehmann, Carl Julius Milde, Philipp Otto Runge, Emil Gottlieb Schuback, Heinrich Stuhlmann, Theodor Bülau, Erwin Speckter, Otto Speckter and Friedrich Wasmann, as well as his own sons, Gerdt (1800-1834), Rudolf [de], and Julius Theodore (1818-1898).