Louis II (825 – 12 August 875), sometimes called the Younger, was the king of Italy and emperor of the Carolingian Empire from 844, co-ruling with his father Lothair I until 855, after which he ruled alone.

Louis's usual title was imperator augustus ("august emperor"), but he used imperator Romanorum ("emperor of the Romans") after his conquest of Bari in 871, which led to poor relations with the Eastern Roman Empire. He was called imperator Italiae ("emperor of Italy") in West Francia while the Byzantines called him Basileus Phrangias ("Emperor of Francia").

The chronicler Andreas of Bergamo, who is the main source for Louis's activities in southern Italy, notes that "after his death a great tribulation came to Italy."