Nietzsche's influence remains substantial within and beyond philosophy, notably in existentialism 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.

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 went insane, living out his remaining years in the care of his mother and sister until his death in 1900.

Born on October 15, 1844, Nietzsche grew up in the small town of Röcken, near Leipzig, in the Prussian Province of Saxony. He was named after King Frederick William IV of Prussia, who turned 49 on the day of Nietzsche's birth. (Nietzsche later dropped his given middle name, "Wilhelm".) Nietzsche's parents, Carl Ludwig Nietzsche (1813–1849), a Lutheran pastor and former teacher, and Franziska Oehler (1826–1897), married in 1843, the year before their son's birth, and had two other children: a daughter, Elisabeth Förster-Nietzsche, born in 1846, and a second son, Ludwig Joseph, born in 1848. Nietzsche's father died from a brain ailment in 1849; his younger brother died in 1850. The family then moved to Naumburg, where they lived with Nietzsche's paternal grandmother and his father's two unmarried sisters. After the death of Nietzsche's grandmother in 1856, the family moved into their own house.

Nietzsche attended a boys' school and then later a private school, where he became friends with Gustav Krug and Wilhelm Pinder, both of whom came from very respected families. In 1854, he began to attend Pforta in Naumburg, but after he showed particular talents in music and language, the internationally recognised Schulpforta admitted him as a pupil, and there he continued his studies from 1858 to 1864. Here he became friends with Paul Deussen and Carl von Gersdorff. He also found time to work on poems and musical compositions. At Schulpforta, Nietzsche received an important introduction to literature, particularly that of the ancient Greeks and Romans, and for the first time experienced a distance from his family life in a small-town Christian environment.

After graduation in 1864 Nietzsche commenced studies in theology and classical philology at the University of Bonn. For a short time he and Deussen became members of the Burschenschaft Frankonia. After one semester (and to the anger of his mother) he stopped his theological studies and lost his faith. This may have happened in part because of his reading around this time of David Strauss's Life of Jesus, which had a profound effect on the young Nietzsche, though in an essay entitled Fate and History written in 1862, Nietzsche had already argued that historical research had discredited the central teachings of Christianity. Nietzsche then concentrated on studying philology under Professor Friedrich Wilhelm Ritschl, whom he followed to the University of Leipzig the next year. There he became close friends with fellow-student Erwin Rohde. Nietzsche's first philological publications appeared soon after.

In 1865 Nietzsche thoroughly studied the works of Arthur Schopenhauer. He owed the awakening of his philosophical interest to reading his Die Welt als Wille und Vorstellung and later admitted that he was one of the few thinkers that he respected, dedicating to him his essay Schopenhauer als Erzieher (Schopenhauer as Educator), one of his Untimely Meditations.

In 1866 he read Friedrich Albert Lange's History of Materialism. Schopenhauer and Lange influenced him. Schopenhauer was especially significant in the development of Nietzsche's later thought. Lange's descriptions of Kant's anti-materialistic philosophy, the rise of European Materialism, Europe's increased concern with science, Darwin's theory, and the general rebellion against tradition and authority greatly intrigued Nietzsche. The cultural environment encouraged him to expand his horizons beyond philology and to continue his study of philosophy.

In 1867 Nietzsche signed up for one year of voluntary service with the Prussian artillery division in Naumburg. However, a riding accident in March 1868 left him unfit for service. Consequently Nietzsche turned his attention to his studies again, completing them and first meeting with Richard Wagner later that year.

In part because of Ritschl's support, Nietzsche received a remarkable offer to become professor of classical philology at the University of Basel. He was only 24 years old and had neither completed his doctorate nor received his teaching certificate. Despite the fact that the offer came at a time when he was considering giving up philology for science, he accepted. To this day, Nietzsche is still among the youngest of the tenured Classics professors on record. Before moving to Basel, Nietzsche renounced his Prussian citizenship: for the rest of his life he remained officially stateless.

Nevertheless, Nietzsche served in the Prussian forces during the Franco-Prussian War of 1870 to 1871 as a medical orderly. In his short time in the military he experienced much, and witnessed the traumatic effects of battle. He also contracted diphtheria and dysentery. Walter Kaufmann speculates that he might also have contracted syphilis along with his other infections at this time, and some biographers speculate that syphilis caused his eventual madness, though there is some disagreement on this matter. On returning to Basel in 1870 Nietzsche observed the establishment of the German Empire and the following era of Otto von Bismarck as an outsider and with a degree of skepticism regarding its genuineness. At the University, he delivered his inaugural lecture, "Homer and Classical Philology". Nietzsche also met Franz Overbeck, a professor of theology, who remained his friend throughout his life. Afrikan Spir, a little-known Russian philosopher and author of Denken und Wirklichkeit (1873), and his colleague the historian Jacob Burckhardt, whose lectures Nietzsche frequently attended, began to exercise significant influence on Nietzsche during this time.