Arizona ( ARR-ih-ZOH-nə; Navajo: Hoozdo Hahoodzo [hoː˥z̥to˩ ha˩hoː˩tso˩]; O'odham: Alĭ ṣonak [ˈaɭi̥ ˈʂɔnak]) is a landlocked state in the Southwestern region of the United States. It is part of the Four Corners region with Utah to the north, Colorado to the northeast, and New Mexico to the east; its other neighboring states are Nevada to the northwest, California to the west and the Mexican states of Sonora and Baja California to the south and southwest. It is the 6th-largest and the 14th-most-populous of the 50 states. Its capital and largest city is Phoenix, which is the most populous state capital in the United States.

Arizona is the 48th state and last of the contiguous states to be admitted to the Union, achieving statehood on February 14, 1912. Historically part of the territory of Alta California and Nuevo México in New Spain, it became part of independent Mexico in 1821. After being defeated in the Mexican–American War, Mexico ceded much of this territory to the United States in 1848, where the area became part of the territory of New Mexico. The southernmost portion of the state was acquired in 1853 through the Gadsden Purchase.

Southern Arizona is known for its desert climate, with very hot summers and mild winters. Northern Arizona features forests of pine, Douglas fir, and spruce trees; the Colorado Plateau; mountain ranges (such as the San Francisco Mountains); as well as large, deep canyons, with much more moderate summer temperatures and significant winter snowfalls.