A toll-free telephone number or freephone number is a telephone number that is billed for all arriving calls. For the calling party, a call to a toll-free number is free of charge, unless air-charges apply for mobile telephone service. A toll-free number is identified by a dialing prefix similar to an area code. The specific service access varies by country.

The features of toll-free services have evolved as telephone networks have evolved from electro-mechanical call switching to computerized stored program controlled networks.

Originally, before the automatic system was developed, a call billed to the called party had to be placed through a telephone company operator as a collect call, often long-distance. The operator had to secure acceptance of the charges at the destination number, or even transfer that decision to a long-distance operator, before manually completing the call.

Some large businesses and government offices received large numbers of collect calls, which proved time-consuming for operators and the callers.

Prior to the development of customer-dialed toll-free service many telephone companies provided the service by operator assistance for telephone subscribers without dial telephones (manual service).

Operator-assisted toll-free calling included the Zenith number service introduced in the 1930s in the U.S. and Canada, as well as the manual 'Freephone' service introduced by the British Post Office in 1960.

Both systems were similar in concept. The calling party would ring the operator (now '100' in the UK, '0' in Canada/U.S.) and ask for a specific free number. In the U.S., the caller would ask for a number like "Zenith 12345" (some areas used "Enterprise" or "WX" instead of "Zenith"). In the UK, the caller would ask the operator to ring "Freephone" and a name or number (such as "Freephone Crimebusters" to pass on tips about a crime to the constabulary).

In either case, the operator would look up the corresponding geographic number from a list and place the call with charges reversed.