The Open University (OU) is the UK's 'open' learning university, established in 1969. The majority of students are based in the UK, but its courses are also studied in the rest of Europe, in Africa and East Asia. The administration is based at Walton Hall, Milton Keynes in Buckinghamshire, but has offices in each of its thirteen regions around the UK. The university awards undergraduate and postgraduate degrees, diplomas and certificates.

With more than 180,000 students enrolled, including more than 25,000 students studying overseas, it is the largest academic institution in the UK by student number, and qualifies as one of the world's mega universities. Since it was founded, more than 3 million students have studied its courses. It was rated top University in England and Wales for student satisfaction in the 2005 and 2006 UK government national student satisfaction survey.