Euclidean theorem

Euclidean theorem may refer to:
 * Any theorem in Euclidean geometry
 * Any theorem in Euclid's Elements, and in particular:
 * Euclid's theorem that there are infinitely many prime numbers
 * Euclid's lemma, also called Euclid's first theorem, on the prime factors of products
 * The Euclid–Euler theorem characterizing the even perfect numbers
 * Geometric mean theorem about right triangle altitude