The EISCAT Scientific Association is an international research organisation operating three incoherent scatter radar systems, at 931 MHz, 224 MHz and 500 MHz, in Northern Scandinavia. It is funded and operated by research councils of Norway, Sweden, Finland, Japan, China and the United Kingdom (collectively, the EISCAT Associates). Germany (until 2011) and France (until 2005) are earlier EISCAT Associates.

EISCAT (European Incoherent Scatter) studies the interaction between the Sun and the Earth as revealed by disturbances in the magnetosphere and the ionised parts of the atmosphere (these interactions also give rise to the spectacular aurora, or Northern Lights). The radars are operated in both Common and Special Programme modes, depending on the particular research objective, and Special Programme time is accounted and distributed between the Associates according to rules which are published from time to time.

One EISCAT transmitter site consisting of a UHF system and a VHF system is located close to the city of Tromsø, in Norway, and additional receiver stations are located in Sodankylä, Finland, and Kiruna, Sweden. The EISCAT Headquarters are also located in Kiruna. In 1996 the EISCAT Scientific Association constructed a second incoherent scatter radar facility, the EISCAT Svalbard Radar (ESR), near Longyearbyen on the island of Spitsbergen, far to the North of the Norwegian mainland.

The Incoherent Scatter Radar requires sophisticated technology and EISCAT engineers are constantly involved in upgrading the systems.

In addition to the incoherent scatter radars, EISCAT also operates an Ionospheric Heater facility at Ramfjordmoen to support various active plasma physics experiments in the high latitude ionosphere, as well as Dynasondes at Ramfjordmoen and on Svalbard.