The Sennar Dam is a dam on the Blue Nile near the town of Sennar, Sudan. It was built during the 1920s by the British contractor, S Pearson & Sons, Ltd, to a design by engineer Sir Murdoch MacDonald. The dam is 3025 meters (9925 feet) long, with a maximum height of 40 meters (130 feet). It provides water for crop irrigation in the Al Jazirah region.