T3 is a Bell System term for a digital carrier facility used for transmission of data through the telephone hierarchy. In North America, T3 service is a digital channel which communicates at approximately 45 Mbps, or 28 T1 lines.

In common usage, the term "T3" is used interchangeably with "DS3", however, T3 historically has been associated more with voice traffic. DS3 is a term more associated with Internet service and data traffic. A T-3 / DS-3 line actually consists of 672 individual channels, each of which supports 64 kbps, that is capable of carrying data at 44,736,000 bits-per-second (44.7 Mbps).

T3 / DS3 can be configured to carry voice, data and video traffic. DS-3 circuits provide businesses and ISP's with up to 45MBps of dedicated Internet connectivity. This is an ideal solution for users who have outgrown their T1 connections and are in search of unlimited, high-capacity access.