Incumbent local exchange carrier

An incumbent local exchange carrier (ILEC) is a local telephone company which held the regional monopoly on landline service before the market was opened to competitive local exchange carriers, or the corporate successor of such a firm. In much of the United States, these were originally Bell System companies, although various regional independents (including GTE) in the US held incumbent monopolies in their respective regions.

In the United States, these were companies in existence at the time of the breakup of AT&T into the Regional Bell Operating Companies (RBOCs), also known as the "Baby Bells."GTE was the second largest ILEC after the Bells, but it has since been absorbed into Verizon, an RBOC. In some areas, an independent telephone company is responsible for providing local telephone exchange services in a specified geographic area.

In Canada, ILECs are the original telephone companies such as Telus (BC Tel and Alberta Government Telephones), SaskTel, Manitoba Telephone Systems (MTS Allstream), Bell Canada and Aliant, as well as any other company that previously held a monopoly to serve a community and continues to do so, or a successor company if it is bought and absorbed. ILECs are obligated to serve the entire exchange area as a "provider of last resort", while CLECs can choose which locations to serve, be it by facilities of their own or by resale of services of an ILEC or another CLEC.

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