Three is a brand name under which several UMTS-based mobile phone networks and Broadband Internet Providers are operated in Australia, Austria, Denmark, Hong Kong, Macau, Indonesia, Ireland, Italy, Sweden, and the United Kingdom. The company was founded in 2002.

CK Hutchison Holdings (formerly Hutchison Whampoa) owns direct majority interests in the companies that operate the networks that are branded 3, except 3 Hong Kong and 3 Indonesia. These networks are majority-owned by Hutchison Asia Telecommunications, a wholly owned subsidiary of CK Hutchison. Its operations in Europe are run by a separate division, 3 Group Europe.

All 3-branded networks provide 4G (LTE) and 3G technology (WCDMA, some also run 2G networks). Hutchison Whampoa no longer holds a 3G licence in Israel which was operated under the brand Orange, and in Norway which is not operational yet. As of 30 June 2015, registered 3 customers worldwide numbered over 30.1 million.