Buffalo Grove is a village in Lake and Cook Counties in the U.S. state of Illinois. A suburb of Chicago, it lies about 30 miles (50 km) northwest of Downtown Chicago and 20 miles (32 km) north of O'Hare International Airport. As of the 2020 Census, Buffalo Grove has a population of 43,212. It totals 9.6 square miles (25 km2) of land, with the top three-quarters in Lake County and the bottom quarter in Cook County. Roads in the village such as Lake Cook Road and Illinois Route 83 converge on I-294. It is part of the Chicago Metropolitan Area.