Friedrich Wilhelm Nietzsche (German pronunciation: [ˈfʁiːdʁɪç ˈvɪlhɛlm ˈniːtsʃə]; in English /ˈniːtʃə/, /-tʃi/) (October 15, 1844 – August 25, 1900) was a 19th-century German philosopher, poet, composer and classical philologist. He wrote critical texts on religion, morality, contemporary culture, philosophy and science, displaying a fondness for metaphor, irony and aphorism.

Nietzsche's influence remains substantial within and beyond philosophy, notably in existentialism, nihilism and postmodernism. His style and radical questioning of the value and objectivity of truth have resulted in much commentary and interpretation, mostly in the continental tradition. His key ideas include the death of God, perspectivism, the Übermensch, the eternal recurrence, and the will to power. Central to his philosophy is the idea of "life-affirmation", which involves an honest questioning of all doctrines that drain life's expansive energies, however socially prevalent those views might be.

Nietzsche began his career as a classical philologist before turning to philosophy. At the age of 24 he was appointed to the Chair of Classical Philology at the University of Basel (the youngest individual to have held this position), but resigned in 1879 due to health problems that plagued him most of his life. In 1889 he became mentally ill, possibly due to atypical general paresis attributed to tertiary syphilis. He lived his remaining years in the care of his mother until her death in 1897, then under the care of his sister until his death in 1900.