Extension theorem

Extension theorem may refer to:

• Carathéodory's extension theorem - a theorem in measure theory, named after the Greek mathematician Constantin Carathéodory
• Hartogs' extension theorem - a theorem in the theory of functions of several complex variables
• Isomorphism extension theorem - a theorem in field theory
• Kolmogorov extension theorem - a theorem in mathematics, named after the Soviet mathematician Andrey Nikolaevich Kolmogorov
• M. Riesz extension theorem - a theorem in mathematics, proved by Marcel Riesz
• Szpilrajn extension theorem - a theorem in set theory, proved by Edward Szpilrajn
• Tietze extension theorem - a theorem in topology
• Urysohn extension theorem - a theorem in topology, named after the mathematician Pavel Samuilovich Urysohn
• Whitney extension theorem - a theorem in mathematical analysis