The Operational Research Society, usually known as The OR Society, is a British educational charity. Originally established in 1948 as the OR Club, it is the world's longest established body in the field, with 3000 members worldwide.

Practitioners of Operational Research (OR) provide advice on complex issues to decision makers in all walks of life, arriving at their recommendations through the application of a wide variety of analytical methods.

The Society's aims are to advance education and knowledge in OR, which it does through the publication of journals, the holding of conferences and meetings, the provision of training courses, and the organisation and support of study (special interest) groups and regional groups. In recent years the Society has made extensive use of internet technologies to facilitate the discovery and exchange of information by its members.