Cartesian means of or relating to the French philosopher René Descartes—from his Latinized name Cartesius. It may refer to:

Mathematics

• Cartesian closed category, a closed category in category theory
• Cartesian coordinate system, modern rectangular coordinate system
• Cartesian diagram, a construction in category theory
• Cartesian geometry, now more commonly called analytic geometry
• Cartesian morphism, formalisation of pull-back operation in category theory
• Cartesian oval, a curve
• Cartesian product, a direct product of two sets
• Cartesian product of graphs, a binary operation on graphs
• Cartesian tree, a binary tree in computer science

Philosophy

• Cartesian anxiety, a hope that studying the world will give us unchangeable knowledge of ourselves and the world
• Cartesian circle, a potential mistake in reasoning
• Cartesian doubt, a form of methodical skepticism as a basis for philosophical rigor
• Cartesian dualism, the philosophy of the distinction between mind and body
  • Cartesianism, the philosophy of René Descartes
  • Cartesianists, followers of Cartesianism
• Cartesian Meditations, a work by Edmund Husserl
• Cartesian linguistics, a work by Noam Chomsky
• Cartesian theatre, a derisive view of Cartesian dualism coined by Daniel Dennett

Science

• Cartesian diver, a science experiment demonstrating buoyancy and the ideal gas law
• Cartesian physics, attempts to explain gravity without a need for action at distance