Mesa is a city in Maricopa County, Arizona, and the third-most populous city in the state with a population of 504,258 at the 2020 census. It ranks as the 38th-most populous city in the United States and is notably the most populous city in the country that is not a county seat. Within the Phoenix metropolitan area, Mesa is the largest city in the East Valley region.
The city is geographically positioned in the eastern part of the Phoenix metropolitan area, bordered by Tempe to the west, the Salt River Pima–Maricopa Indian Community to the north, and Chandler, Gilbert, and Queen Creek to the south. Apache Junction lies to the east of Mesa.