三河國
was a Japanese feudal domain under the Tokugawa shogunate of Edo period Japan, located in Mikawa Province located in eastern Mikawa Province (modern-day eastern Aichi Prefecture), Japan. It was centered on Yoshida Castle in what is now the city of Toyohashi, Aichi. It was ruled by a number of different "fudai daimyō" over the course of the Edo period, before finally passing into the hands of the Matsudaira (Ōkōchi) clan. Just before its dissolution it was renamed, and it became the .