Mutsu (陸奥国; -no kuni) is an old province of Japan, which today composes Fukushima, Miyagi, Iwate and Aomori prefectures and the city of Kazuno and the town of Kosaka in Akita prefecture.　Also known as Ōshū (奥州).

Mutsu, in northern Honshu, was one of the last provinces to be formed as land was taken from the indigenous Ainu, and became the largest as it expanded northward. The ancient capital was in modern Miyagi prefecture. During the Sengoku period various clans ruled different parts of the province. The Uesugi clan had a castle town at Wakamatsu in the south, the Nambu clan at Morioka in the north, and Date Masamune, a close ally of the Tokugawa, established Sendai, which is now the largest town of the Tohoku region.

During the Meiji period, four other provinces were created from parts of Mutsu, including Rikuchu, Rikuzen, Iwaki, and Iwashiro. The area that is now Aomori Prefecture continued to be part of Mutsu until the Abolition of the Han system.