Baruch (de) Spinoza (24 November 1632 – 21 February 1677) was a philosopher of Portuguese-Jewish origin, born in Amsterdam, the Dutch Republic, and mostly known under the Latinized pen name Benedictus de Spinoza. One of the foremost and seminal thinkers of the Enlightenment, modern biblical criticism, and 17th-century Rationalism, including modern conceptions of the self and the universe, he came to be considered "one of the most important philosophers—and certainly the most radical—of the early modern period". Inspired by Stoicism, Jewish Rationalism, Machiavelli, Hobbes, Descartes, and a variety of heterodox religious thinkers of his day, Spinoza became a leading philosophical figure in Dutch Golden Age.

Spinoza was raised in the Portuguese-Jewish community of Amsterdam. He developed highly controversial ideas regarding the authenticity of the Hebrew Bible and the nature of the Divine. Jewish religious authorities issued a herem (חרם‎) against him, causing him to be effectively expelled and shunned by Jewish society at age 23, including by his own family. He was frequently called an "atheist" by contemporaries, although nowhere in his work does Spinoza argue against the existence of God. Spinoza lived an outwardly simple life as an optical lens grinder, collaborating on microscope and telescope lens designs with Constantijn and Christiaan Huygens. He turned down rewards and honours throughout his life, including prestigious teaching positions. He died at the age of 44 in 1677 from a lung illness, perhaps tuberculosis or silicosis exacerbated by the inhalation of fine glass dust while grinding lenses. He is buried in the Christian churchyard of Nieuwe Kerk in The Hague. In June 1678—just over a year after Spinoza's death—the States of Holland banned his entire works, since they "contain very many profane, blasphemous and atheistic propositions." The prohibition included the owning, reading, distribution, copying, and restating of Spinoza's books, and even the reworking of his fundamental ideas. Shortly after (1679/1690) his books were added to the Catholic Church's Index of Forbidden Books.

Spinoza's philosophy encompasses nearly every area of philosophical discourse, including metaphysics, epistemology, political philosophy, ethics, philosophy of mind, and philosophy of science. It earned Spinoza an enduring reputation as one of the most important and original thinkers of the seventeenth century. Spinoza's philosophy is largely contained in two books: the Theologico-Political Treatise, and the Ethics. The rest of the writings we have from Spinoza are either earlier or incomplete works expressing thoughts that were crystallized in the two aforementioned books (e.g., the Short Treatise and the Treatise on the Emendation of the Intellect), or else they are not directly concerned with Spinoza's own philosophy (e.g., The Principles of Cartesian Philosophy and The Hebrew Grammar). He also left behind many letters that help to illuminate his ideas and provide some insight into what may have been motivating his views. The Theologico-Political Treatise was published during his lifetime, but the work which contains the entirety of his philosophical system in its most rigorous form, the Ethics, was published posthumously in the year of his death. The work opposed Descartes's philosophy of mind–body dualism and earned Spinoza recognition as one of Western philosophy's most important thinkers.