Matsudaira Sadayasu (松平 定安, May 5, 1835 – December 1, 1882) was a Japanese daimyō of the late Edo period, who ruled the Matsue Domain.

During Sadayasu's tenure as lord, Matsue samurai were deployed to security duties in Osaka and Kyoto.

The same year, there was a peasant revolt in the Oki Islands, which was part of Matsue territory.

Sadayasu dispatched troops to quell it by force; he withdrew after receiving complaints from Satsuma and Chōshū.

Sadayasu was relieved of his duties as daimyō in 1871, due to the order for the abolition of the domains.