The Satcho Alliance (薩長同盟: Satchō dōmei) was the alliance between Satsuma and Choshu formed in 1866. The name Satcho (薩長) is an abbreviation combining the names of the provinces Satsuma (薩摩) and Choshu (長州), two of the strongest anti-shogunate domains before and during the Meiji Restoration in Japan.

The two domains were traditionally fierce enemies, but their leaders, in particular Saigo Takamori and Okubo Toshimichi of Satsuma and Katsura Kogoro (Kido Takayoshi) of Choshu, were brought together against the Tokugawa Shogunate through the mediation of Sakamoto Ryoma. In Japanese history the above three personages are collectively known as the Ishin-no-Sanketsu or the 'Three Great Restorers.'