Buckeye is a city in Maricopa County, Arizona, United States. It is Arizona's second-largest city by area, and it is the westernmost suburb in the Phoenix Metropolitan Area. As of the 2020 census, the population was 91,502, up from 50,876 in 2010, and 6,537 in 2000. It was the fastest-growing city in the United States for 2017, 2018, and 2021.