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.
Kalthoff criticized what he regarded as the romanticist and sentimental image of Jesus as a "great personality" of history developed by German liberal theologians, including Albert Schweitzer who noted Kalthoff in his work The Quest of the Historical Jesus.
However his scholarship was buried by German academia, and he remained a pariah, until Albert Kalthoff rescued his works from neglect and obscurity.
Kalthoff revived Bruno Bauer's Christ Myth thesis in his Das Christus-Problem.
Grundlinien zu einer Sozialtheologie (The Problem of Christ: Principles of a Social Theology) and Die Entstehung des Christentums, Neue Beiträge zum Christusproblem (The Rise of Christianity).