The Buchan oil field is a small oil field with small gas reserves in the central North Sea. It lies in an area known as the South Halibut Basin, approximately 120 miles (190 km) northeast of Aberdeen, Scotland, and is located mainly in license block 21/1A, extending into block 20/5A(E). The field was discovered in August 1974, two years after the issue date for those blocks. It is named after Buchan, an area of N.E. Scotland with its main town being Peterhead.

Buchan was initially considered a very risky field, both commercially and operationally, and was expected to be finished with after five years. The field's geology created significant difficulties at the start of its development, but the development of new drilling and extraction technology has made possible a continuing increase in its recoverable reserves. It is thought that Buchan will continue to play an important part in the North Sea and that further technological breakthroughs will allow continued production of this field to at least 2018.