Janet is a high-speed network for the UK research and education community provided by Jisc, a not-for-profit company set up to provide computing support for education. It serves 18 million users and is the busiest National Research and Education Network in Europe by volume of data carried. Previously, Janet was a private, UK-government funded organisation, which provided the JANET computer network and related collaborative services to UK research and education.

All further- and higher-education organisations in the UK are connected to the Janet network, as are all the Research Councils; the majority of these sites are connected via 20 metropolitan area networks across the UK (though Janet refers to these as regions, emphasising that Janet connections are not just confined to a metropolitan area). The network also carries traffic between schools within the UK, although many of the schools' networks maintain their own general Internet connectivity. The name was originally a contraction of Joint Academic NETwork but it is now known as Janet in its own right.

The network is linked to other European and worldwide NRENs through GÉANT and peers extensively with other ISPs at Internet Exchange Points in the UK. Any other networks are reached via transit services from commercial ISPs using Janet's Peering Policy.

The Janet network is operated by Jisc Services Limited, part of Jisc. Janet is also responsible for the .ac.uk and .gov.uk domains. On 1 December 2012, Janet and Jisc Collections joined together to form Jisc Collections and Janet Limited, as subsidiary organisations to Jisc. In March 2015, Jisc Collections and Janet Limited was renamed to Jisc Services Limited. Jisc Services continues to operate under the brand name of Janet, with the same remit. Janet was previously known as the JNT Association, and prior to that, UKERNA (the United Kingdom Education and Research Networking Association).