Galion is located in the southeastern corner of Crawford County at 40°43′59″N 82°47′19″W / 40.73306°N 82.78861°W / 40.73306; -82.78861 (40.733164, -82.788586).

According to the United States Census Bureau, the city has a total area of 5.0 square miles (12.9 km²), of which, 5.0 square miles (12.8 km²) of it is land and 0.20% is water.

The most important river in Galion is the Olentangy, which winds southward toward Columbus and eventually empties into the Scioto River. In Galion, the Olentangy is not a very large river, though another creek joins it near Heise Park.

As of the census of 2000, there were 11,341 people, 4,791 households, and 3,090 families residing in the city. The population density was 2,286.5 people per square mile (882.8/km²). There were 5,150 housing units at an average density of 1,038.3/sq mi (400.9/km²). The racial makeup of the city was 98.28% White, 0.22% African American, 0.31% Native American, 0.26% Asian, 0.01% Pacific Islander, 0.35% from other races, and 0.56% from two or more races. Hispanic or Latino of any race were 0.93% of the population.

There were 4,791 households out of which 31.0% had children under the age of 18 living with them, 48.3% were married couples living together, 12.2% had a female householder with no husband present, and 35.5% were non-families. 30.7% of all households were made up of individuals and 13.6% had someone living alone who was 65 years of age or older. The average household size was 2.34 and the average family size was 2.90.

In the city the population was spread out with 25.5% under the age of 18, 8.5% from 18 to 24, 27.8% from 25 to 44, 22.2% from 45 to 64, and 16.0% who were 65 years of age or older. The median age was 37 years. For every 100 females there were 85.6 males. For every 100 females age 18 and over, there were 82.7 males.

The median income for a household in the city was $31,513, and the median income for a family was $38,554. Males had a median income of $32,517 versus $19,792 for females. The per capita income for the city was $16,113. About 11.9% of families and 14.7% of the population were below the poverty line, including 19.6% of those under age 18 and 11.3% of those age 65 or over.

Galion has a council-manager government: it is governed by an elected city council, which hires a city manager in lieu of an elected mayor.

The Galion City School District encompasses the entire city of Galion, graduating about 170 students annually. There are a handful of neighborhoods outside of Galion that are also included in the school district, including Blooming Grove, birthplace of Warren G. Harding.

Settlers arrived in the area as early as 1817. The location was at the crossroads of a north-south road from Columbus to Portland (now known as Sandusky), and the east-west route that later became (part of) the Lincoln Highway and subsequently the Harding Highway.