German philosophy, meaning philosophy in the German language or philosophy by German people, in its diversity, is fundamental for both the analytic and continental traditions. It covers figures such as Gottfried Wilhelm Leibniz, Immanuel Kant, Georg Wilhelm Friedrich Hegel, Karl Marx, Friedrich Nietzsche, Martin Heidegger, Ludwig Wittgenstein, the Vienna Circle, and the Frankfurt School, who now count among the most famous and studied philosophers of all time. They are central to major philosophical movements such as rationalism, German idealism, Romanticism, dialectical materialism, existentialism, phenomenology, hermeneutics, logical positivism, and critical theory. The Danish philosopher Søren Kierkegaard is often also included in surveys of German philosophy due to his extensive engagement with German thinkers.

In his writings, Albertus Magnus covers a wide range of topics in science and philosophy.

Jakob Böhme (1575–1624), the Lutheran philosopher who founded Christian theosophy, influenced later key figures including F.W.J. Schelling and G.W.F. Hegel, who called him "the first German philosopher".

Gottfried Wilhelm Leibniz (1646–1716) was both a philosopher and a mathematician who wrote primarily in Latin and French. Leibniz, along with René Descartes and Baruch Spinoza, was one of the three great 17th century advocates of rationalism. The work of Leibniz also anticipated modern logic and analytic philosophy, but his philosophy also looks back to the scholastic tradition, in which conclusions are produced by applying reason to first principles or a priori definitions rather than to empirical evidence.

Leibniz is noted for his optimism – his Théodicée tries to justify the apparent imperfections of the world by claiming that it is optimal among all possible worlds. It must be the best possible and most balanced world, because it was created by an all powerful and all knowing God, who would not choose to create an imperfect world if a better world could be known to him or possible to exist. In effect, apparent flaws that can be identified in this world must exist in every possible world, because otherwise God would have chosen to create the world that excluded those flaws.

Leibniz is also known for his theory of monads, as exposited in Monadologie. They can also be compared to the corpuscles of the mechanical philosophy of René Descartes and others. Monads are the ultimate elements of the universe. The monads are "substantial forms of being" with the following properties: they are eternal, indecomposable, individual, subject to their own laws, un-interacting, and each reflecting the entire universe in a pre-established harmony (a historically important example of panpsychism). Monads are centers of force; substance is force, while space, matter, and motion are merely phenomenal.

Christian Wolff (1679–1754) was the most eminent German philosopher between Leibniz and Kant. His main achievement was a complete oeuvre on almost every scholarly subject of his time, displayed and unfolded according to his demonstrative-deductive, mathematical method, which perhaps represents the peak of Enlightenment rationality in Germany.

Wolff was one of the first to use German as a language of scholarly instruction and research, although he also wrote in Latin, so that an international audience could, and did, read him. A founding father of, among other fields, economics and public administration as academic disciplines, he concentrated especially in these fields, giving advice on practical matters to people in government, and stressing the professional nature of university education.