Zhang Sixun (fl.

10th century) is a Chinese astronomer and military engineer from Bazhong, Sichuan during the early Song Dynasty (960-1279).

He is credited with creating an armillary sphere for his astronomical clock tower that employs the use of liquid mercury (dripped periodically from a clepsydra clock).

The liquid mercury-filled scoops of the waterwheel would rotate and thus provide the effect of an escapement mechanism in clockworks and allow the astronomical armillary sphere to rotate as needed.

He designs the model for his armillary sphere in 976 and completes the creation of it in 977.