Boso (; c. 841 – 11 January 887) was a Frankish nobleman of the Bosonid family who was related to the Carolingian dynasty and who rose to become King of Lower Burgundy and Provence. Origin Boso was the son of Bivin of Gorze, count of Lotharingia, by Richildis, the daughter of Boso the Elder by his wife Engeltrude. His maternal aunt Teutberga was the wife of King Lothair II of Lotharingia. Boso was also the nephew of Count Boso of Valois, for whom he was named, and of Hucbert, lay abbot of St. Maurice's Abbey, to which Boso succeeded in 869. Countship In 870, King Charles the Bald of West Francia married Boso's sister Richilde. This marriage paved the way for Boso's career in the service of his royal brother-in-law. In the same year, Boso was appointed count of Lyon and Vienne, replacing Gerard of Roussillon. In 872, Charles appointed him chamberlain and magister ostiariorum (master of porters) to his heir Louis the Stammerer. Boso likewise received investiture as count of Bourges. Louis was reigning as a subordinate king of Aquitaine, but because of his youth, it was Boso who looked after the administration of that realm. In the autumn of 875, Boso accompanied Charles on his first Italian campaign and at the diet of Pavia in February 876 he was appointed arch-minister and missus dominicus for Italy and elevated to the rank of duke. He became governor and count of Provence in 877. He acted as a viceroy and married Ermengarde, the only daughter of Emperor Louis II. Boso disapproved of Charles' second Italian campaign in 877 and conspired with other like-minded nobles against his king. After Charles's death in October, these nobles forced Charles's son to confirm their rights and privileges. Boso also formed close relations to the papacy and accompanied Pope John VIII in September 878 to Troyes, where the Pope asked King Louis for his support in Italy. The Pope adopted Boso as his son and probably offered to crown Louis emperor. It is said that he wanted to crown Boso emperor. Kingship In April 879, Louis the Stammerer died, leaving two adult sons, Louis III and Carloman II. Boso joined with other western Frankish nobles and advocated making Louis III the sole heir of the western kingdom, but eventually both brothers were elected kings. Boso renounced allegiance to the brothers and in July claimed independence