A telephone plug is a type of male connector used to connect a telephone to the telephone wiring in a home or business, and in turn to a local telephone network. It is inserted into its female counterpart, a telephone "jack", commonly fixed to a wall or baseboard. The standard for telephone plugs varies from country to country, though the RJ11 "modular connector" has become by far the most common.

A connection standard, such as "RJ11", specifies not only the physical connector, but how it is wired (the "pinout"). Modular connectors are specified for the Registered Jack series of connectors, as well as for Ethernet and other connectors, such as 4P4C (4 position, 4 contacts) modular connectors, the de facto standard on handset cables, often improperly referred to as "RJ connectors".

History

Historically the telephone was often owned by the supplier and permanently wired in to the telephone line they supplied but as phone markets became more deregulated there was a need for a simple plug-in interface that consumers could use. Many countries initially used their own connectors. For example Bell System companies in the 1960s used a round plug about 40mm in diameter with four prongs about 15mm apart. National connectors remain in service but few are used for new installations.