Moriyama is located on the south side of the alluvial fan where the Yasu River flowing from the Suzuka Mountains enters into Lake Biwa.

Shiga Prefecture Moriyama has a Humid subtropical climate (Köppen Cfa) characterized by warm summers and cool winters with light to no snowfall.

The area contains many archaeological sites from the Jōmon and especially the Yayoi period, and the Yasu River has been a key point for east-west transportation since ancient times.

The village of Moriyama was stablished within Yasu District, Shiga on April 1, 1889 with the creation of the modern municipalities system.

Moriyama has a mayor-council form of government with a directly elected mayor and a unicameral city council of 22 members.

However, due to its location and transportation connections, the population growth of the city has been primarily as a commuter town to the nearby Kyoto, Osaka and Ōtsu urban areas.