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.

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

In terms of national politics, the city is part of Shiga 3rd district of the lower house of the Diet of Japan.

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.