Carl Justi (2 August 1832, in Marburg – 9 December 1912, in Bonn) was a German art historian, who practised a biographical approach to art history. Professor of art history at the University of Bonn, he wrote three major critical biographies: of Johann Joachim Winckelmann, of Diego Velázquez and of Michelangelo.
Born in Marburg, Justi studied theology at the University of Berlin before transferring to philosophy. He graduated in 1859 with a thesis 'Über die ästhetischen Elemente in der platonischen Philosophie'.
Justi established his reputation with a three-volume work on Johann Joachim Winckelmann. He succeeded Anton Springer in the chair of art history at the University of Bonn, holding the post from 1872 until 1901.