Friedrich Nietzsche was an influential German philosopher of the late 19th century who challenged traditional morality and religion. He developed key philosophical concepts like the will to power, eternal recurrence, and the √úbermensch, while critiquing Christianity and advocating for a revaluation of all values. Nietzsche's major works include "Thus Spoke Zarathustra," "Beyond Good and Evil," and "On the Genealogy of Morals," which continue to have a significant impact on Western philosophy and culture.