Lothair II (926/8 – 22 November 950), often Lothair of Arles, was the King of Italy from 948 to his death. He was of the noble Frankish lineage of the Bosonids, descended from Boso the Elder. His father and predecessor was Hugh of Provence, great grandson of Lothair II, King of Lotharingia, and his mother was a German princess named Alda (or Hilda).
Although he held the title of rex Italiae, he never succeeded in exercising power there. He was betrothed in 931 and married, 12 December 947, to the fifteen-year-old Adelaide, the spirited and intelligent daughter of Rudolph II of Burgundy and Bertha of Swabia.
Their marriage was part of a political settlement designed to conclude a peace between her father and his. In 933, Hugh of Arles had given up his kingdom (Provence) to his inveterate enemy Rudolph II, who merged the two kingdoms into a new Kingdom of Arles, but died in 937. The couple had a daughter, Emma, born as early as 948, who was married in 966 to the Carolingian Lothair of France.
Lothair's power in Italy was nominal. From the time of the successful uprising of the nobles in 945, when Hugh was forced into exile, Berengar of Ivrea kept all real power and patronage in his hands. Lothair died at Turin, perhaps poisoned by Berengar, who attempted to cement his usurped political power in Lombardy by forcing Lothair's widow to marry his son Adalbert. Instead she entreated the protection of Otto I of Germany, whom she married.
Lothair figures briefly in the vita of Adelaide written by Hroswitha of Gandersheim.