In geometry, a chiliagon (pronounced ) is a polygon with 1000 sides. The measure of each angle in a regular chiliagon is 179.64°.

René Descartes uses the chiliagon as an example in his Sixth meditation to demonstrate the difference between pure intellection and imagination. He says that, on imagining a chiliagon, the image produced is not as clear and distinct as that which occurs on imagining a triangle, for example. It is also no different from that of a myriagon. However, he does understand what a chiliagon is, just as he understands what a triangle is. Therefore, the imagination must in some way different from the mind, Descartes claims.

See also

Polygons