The Azai clan was a line of daimyōs (feudal military lords) seated at Odani Castle in northeastern Ōmi Province, located within present day Nagahama, Shiga Prefecture.

[1] Initially, the clan were vassals of the Kyōgoku, but gradually emerged as independent daimyōs in northern Ōmi.

[1] However, Azai domains were soon conquered by the Rokkaku and the clan was forced into becoming their vassals.

Azai Nagamasa became head of the clan in 1560 and successfully fought against the Rokkaku for independence by 1564.

In 1570, Nagamasa joined the Asakura in their opposition to lord Oda Nobunaga, his brother-in-law and ally, to honour their alliance.