In geometry, the Császár polyhedron is a nonconvex toroidal polyhedron with 14 triangular faces.

This polyhedron has no diagonals; every pair of vertices is connected by an edge. Of the 35 possible triangles from vertices of the polyhedron, only 14 are faces.

The tetrahedron and the Császár polyhedron are the only two known polyhedra without any diagonals: every two vertices of the polygon are connected by an adge, so there is no line segment between two vertices that does not lie on the polyhedron boundary.