Delavan is a city in Tazewell County, Illinois, United States. Its population was 1,689 in the 2010 census. It is a part of the Peoria, Illinois Metropolitan Statistical Area.

Tazewell County is a county in the U.S. state of Illinois. According to the 2020 census, it had a population of 131,343. Its county seat and largest city is Pekin. It is pronounced with a short "a", to rhyme with "razz" rather than "raze."