Albert Kalthoff (5 March 1850, Barmen – 11 May 1906, Bremen) was a German Protestant theologian, who along with Emil Felden (1874-1959), Oscar Mauritz (1867-1959), Moritz Schwalb (1833-1916) and Friedrich Steudel (1866-1939) formed a group in Bremen, named the Deutscher Monistenbund (German Monists League), who no longer believed in Jesus as a historical figure.