Ariel 3 (UK 3 or United Kingdom Research Satellite 3) was a satellite in the Ariel programme, a satellite partnership between the US and UK. Three of the onboard experiments continued research from the first two missions and two experiments were designed for new research topics. It was launched from Vandenberg Air Force Base on 5 May 1967, making it the first satellite of the program to launch from the West coast. Ariel 3 was shut down in September 1969, and re-entered the Earth's atmosphere 14 December 1970.

This was the first artificial satellite designed and constructed in the United Kingdom.