Born in Geesthacht, Ritter studied philosophy, theology, German literature, and history in Heidelberg, Marburg, Freiburg and Hamburg. A disciple of Martin Heidegger and Ernst Cassirer, he obtained his doctorate with a dissertation on Nicolas of Cusa in 1925. Ritter was Cassirer's assistant and a lecturer at the University of Hamburg. A Marxist in the late 1920s and early 1930s, he became a member of the Nazi Party in 1937 and an officer of the German Wehrmacht in 1940. After World War II, Ritter was appointed professor of philosophy in Münster.
Ritter's philosophical work focuses on a theory of modernity. In a liberal interpretation of Hegel's Philosophy of Right, he developed the view that "bifurcation" is the constitutive structure of the modern world and a necessary precondition for the universal realization of individual freedom. According to Ritter's theory of culture as compensation, arts and humanities have the function of balancing the disenchanted, ahistorical condition of modern society. Alongside Hans-Georg Gadamer, his work on Aristotle's ethics and political theory initiated the renewal of practical philosophy in Germany.
Ritter is considered one of the most influential philosophers in postwar Western Germany. Among his disciples were scholars and public intellectuals like Ernst-Wolfgang Böckenförde, Max Imdahl, Hermann Lübbe, Odo Marquard, and Robert Spaemann. Together with them, Ritter started the „Historisches Wörterbuch der Philosophie“ and contributed to development of conceptual history in the field of philosophy. In the 1980s, Jürgen Habermas opposed the Ritter-School for being leading representatives of German neo-conservatism. More recent scholarship in intellectual history points out Ritter's seminal role for the modernization of German political thought and the development of a modern liberal republicanism.