The Duchy of Rethel was a historical territory in northeastern France, established in the early 10th century. It was part of the larger region of Champagne and played a significant role in the feudal system of the time. The duchy was known for its strategic location and was often contested by various noble families. The duchy was ruled by a series of dukes, with notable figures including Hugh of Rethel. Over time, the importance of the duchy diminished, and it eventually became integrated into the County of Champagne and later the Kingdom of France.