Founder of the Ernestine line of Saxon princes, ancestor of Prince Consort, born at Altenburg; was kidnapped along with his brother Albert in 1455, an episode famous in German history as the "Prinzenraub" (i. e. the stealing of the prince); succeeded his father in 1464; annexed Thuringia in 1482, and three years later shared his territory with his brother Albert (1441-1486).