A United Kingdom tells the true story of Seretse Khama, heir to the throne of Bechuanaland (modern-day Botswana), who falls in love with and marries Ruth Williams, a white British woman, in the late 1940s. Their union sparks international controversy, facing fierce opposition from both the British government and Khama’s own people. Despite political and racial pressures, Seretse and Ruth’s love and determination transform their struggle into a fight for equality, independence, and the future of Botswana.