Louis II (825 – 12 August 875), sometimes called the Younger,[1] 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.

Little is known about his early life, except that he grew up in his grandfather's court and probably developed a warm affection for the emperor who, in 839, designated his grandson as King of Italy, and let Louis take up his residence in that country.

He marched into the south of Italy in the year of his imperial coronation and compelled the rival dukes of Benevento, Radelchis I and Siconulf, to make peace.

His mediation split the Lombard duchy and gave Radelchis his share with Benevento as his capital, whilst Salerno was given to Siconulf as an independent principality.

But after Louis had secured the election of Pope Nicholas I in 858, he reconciled with his brother, and received some lands south of the Jura mountains in return for assistance given to Lothair in his efforts to obtain a divorce from his wife, Teutberga.

The archbishops, who had been deposed by Nicholas for proclaiming this marriage invalid, obtained the support of the emperor, who reached Rome with an army in February 864; but, having been seized with fever, he made peace with the pope and left the city.

The landing of fresh bands of Aghlabids compelled Adelchis to release his prisoner a month later, and Louis was forced to swear he would take no revenge for this injury, nor ever enter Benevento with an army.