René Descartes (; Latinized form: Renatus Cartesius; adjectival form: "Cartesian"; 31 March 1596 – 11 February 1650) was a French philosopher, mathematician, and writer who spent most of his adult life in the Dutch Republic. He has been dubbed the 'Father of Modern Philosophy', and much subsequent Western philosophy is a response to his writings, which are studied closely to this day. In particular, his Meditations on First Philosophy continues to be a standard text at most university philosophy departments. Descartes' influence in mathematics is equally apparent; the Cartesian coordinate system — allowing algebraic equations to be expressed as geometric shapes in a two-dimensional coordinate system — was named after him. He is credited as the father of analytical geometry, the bridge between algebra and geometry, crucial to the discovery of infinitesimal calculus and analysis. Descartes was also one of the key figures in the Scientific Revolution and has been described as an example of genius.

René Descartes [] (latinisiert Renatus Cartesius; * 31. März 1596 in La Haye/Touraine, Frankreich; † 11. Februar 1650 in Stockholm, Schweden) war ein französischer Philosoph, Mathematiker und Naturwissenschaftler.

René Descartes, né à La Haye en Touraine aujourd'hui dénommée Descartes le et mort à Stockholm dans le glacial palais royal de Suède le , est un mathématicien, physicien et philosophe français. Plus qu'un penseur scientifique, cet observateur singulier en son temps, contemporain de Poussin, est considéré comme l'un des fondateurs de la philosophie moderne.

Den här artikeln handlar om filosofen René Descartes. För kommunen i Frankrike, se Descartes, Indre-et-Loire. För dikten om honom, se Cartesius (dikt).

Kartezjusz (fr. René Descartes, łac. Renatus Cartesius), (ur. 31 marca 1596 r. w La Haye-en-Touraine (obecnie Descartes) w Turenii, zm. 11 lutego 1650 r. w Sztokholmie) – francuski matematyk, filozof i fizyk, jeden z najwybitniejszych uczonych XVII w., uważany za prekursora nowożytnej kultury umysłowej.