Yamashiro Province (山城国 Yamashiro no Kuni?) was a province of Japan, located in Kinai. It overlaps the southern part of modern Kyoto Prefecture on Honshū. Aliases include Jōshū (城州?), the rare Sanshū (山州?), and Yōshū (雍州?). It is classified as an upper province in the Engishiki.
Yamashiro Province included Kyoto itself, as in 794 AD Yamashiro became the seat of the imperial court, and, during the Muromachi period, was the seat of the Ashikaga shogunate as well. The capital remained in Yamashiro until its de facto move to Tokyo in the 1870s.
"Yamashiro" was formerly written with the characters meaning "mountain" () and "area" (); in the 7th century, there were things built listing the name of the province with the characters for "mountain" and "ridge"/"back" (). On 4 December 794 (8 Shimotsuki, 13th year of Enryaku), at the time of the christening of Heian-kyō, because of the resultant scenic beauty when Emperor Kanmu made his castle utilizing the natural surroundings, the shiro was finally changed to "castle" ().