Rhys ap Gruffydd stands out from his fellow Welsh rulers, not simply on account of his singular appellation as The Lord Rhys, but because of some indefinable quality which marked him as a prince of unusual talent, vision and insight. Here was a native ruler whose long and varied career touched on twelfth-century Welsh and Marcher society at many points: he was an astute politician, a zealous reformer, a sensitive patron of the arts and a warrior of distinction. But above all, he was the architect of peaceful coexistence. It is fitting that in the eighth centenary of his death in 1197, the life and achievements of the Lord Rhys are now reassessed. This study serves to emphasize his significance as one of the more remarkable and fascinating figures in the history of medieval Wales.