Charsianon (Greek: Χαρσιανόν) was the name of a Byzantine fortress and the corresponding theme (a military-civilian province) in the region of Cappadocia in eastern Anatolia (modern Turkey).

[1] The fortress is now identified with the ruins of Muşalikalesi (Muşali Kale of old) in the Akdağmadeni district in Yozgat Province.

[1][4] It ranked in the middle tier of themes, with its governing strategos receiving an annual salary of 20 pounds of gold and commanding, according to Arab sources, 4,000 men and four fortresses.

[1] In the 10th century, the theme of Charsianon became a major stronghold of the landed military aristocracy, with the great clans of Argyros and Maleinos having their homes and estates there.

After 1045, a large number of Armenians, including the former king Gagik II (r. 1042–1045), were settled there, leading to friction with the local Greeks.