Circle theorem

Circle theorem may refer to:
 * Any of many theorems related to the circle; often taught as a group in GCSE mathematics. These include:
 * Inscribed angle theorem.
 * Thales' theorem, if A, B and C are points on a circle where the line AC is a diameter of the circle, then the angle ∠ABC is a right angle.
 * Alternate segment theorem.
 * Ptolemy's theorem.
 * The Milne-Thomson circle theorem in fluid dynamics.
 * Five circles theorem
 * Six circles theorem
 * Seven circles theorem
 * Gershgorin circle theorem