In mathematics, a **right circular cone** is the surface, located in the three dimensional space, formed by rotating one lines about another line that intersects it at an angle that is not the right angle. The point where the two lines intersect is the vertex.

The intersection of a plane with this object forms an important set of two dimensional curves, called the conic sections.

Cones in general do not have to be "right" or "circular", and may be truncated, i.e., not extend to infinity. A familiar example of a (doubly) truncated cone is a basketball net.

The volume of a cone is equal to the product of the base, height, and one third.