Lothair, sometimes called Lothair II, III or IV, was the penultimate Carolingian king of West Francia, reigning from 10 September 954 until his death in 986.

In medieval historiography, West Francia or the Kingdom of the West Franks constitutes the initial stage of the Kingdom of France and extends from the year 843, from the Treaty of Verdun, to 987, the beginning of the Capetian dynasty. It was created from the division of the Carolingian Empire following the death of Louis the Pious, with its neighbor East Francia eventually evolving into the Kingdom of Germany.