Aledo is a city in Mercer County, Illinois, United States. The population was 3,613 at the 2000 census. It is the county seat of Mercer County.
Aledo is located at 41°12′1″N 90°45′0″W / 41.20028°N 90.75°W / 41.20028; -90.75 (41.200172, -90.749956).
According to the United States Census Bureau, the city has a total area of 2.3 square miles (5.9 km²), of which, 2.2 square miles (5.8 km²) of it is land and 0.44% is water.