In the U.S. state of Arizona, Interstate 10 (I‑10), the major east–west Interstate Highway in the United States Sun Belt, runs east from California, enters Arizona near the town of Ehrenberg and continues through Phoenix and Tucson and exits at the border with New Mexico near San Simon. The highway also runs through the cities of Casa Grande, Eloy, and Marana. Segments of the highway are referred to as either the Papago Freeway, Inner Loop, or Maricopa Freeway within the Phoenix area, and the Pearl Harbor Memorial Highway outside metro Phoenix.
The western terminus is located at the California border at the Colorado River in La Paz County where I-10 continues westward into California towards Los Angeles. Here, the same physical road is signed as both I‑10 and U.S. Route 95 (US 95).
The highway runs east by northeast past Ehrenberg and Quartzsite and then turns to an east by southeast orientation just before the junction for US 60. It continues this path entering Maricopa County and the Phoenix Metro area. The route turns east by northeast again at the junction for State Route 85 (SR 85) northwest of downtown Buckeye, and turns due east at Verrado Way (exit 120). Here, the speed limit drops from 75 to 65 miles per hour (121 to 105 km/h). The landscape by this point is largely urban.
From there, I-10 traverses through the communities of Goodyear, Avondale and Tolleson, meeting with local streets and area freeways such as the Loop 303 Estrella Freeway (at the former Cotton Lane interchange, exit 124) and the Loop 101 Agua Fria Freeway along the way. By October 2018, the simple diamond interchange with 59th Avenue (exit 138) will have been totally rebuilt, transforming it into the first of three junctions with Loop 202 (here known as the South Mountain Freeway). As it makes its way through Phoenix, the highway meets with I‑17 and US 60 for the first time just northwest of downtown at The Stack.
East of The Stack, I-10 forms the north edge of downtown. Near 3rd Avenue, the highway enters a half-mile tunnel (800 m) that runs under a park and the central branch of the City of Phoenix Library. Emerging past 3rd Street, the highway continues due eastward for another 2 miles (3.2 km) before coming to another interchange for Route 51 and Loop 202 (second of three junctions with the latter), called the Mini Stack. At this interchange, I‑10 turns southward for about 3 miles (4.8 km), passing near Sky Harbor Airport and reaching the second junction with I‑17/US 60. Here, I‑17 terminates as I‑10 skews eastward again. After this junction, the highway is co-signed with US 60.
Continuing southeast over the Salt River and eastward, I‑10 and US 60 enter Tempe and meets with SR 143. Then, at the Broadway Curve, the freeway turns southward again, with US 60 splitting off to become its own freeway. I‑10 continues southward running along the city borders of Phoenix on the west, and Tempe, Guadalupe, Tempe again, and finally Chandler on the east. Immediately north of the Gila River Indian Community, I‑10 has its third and final intersection with Loop 202. Past Loop 202, the highway turns to a more south by southeast direction going through the Gila River Indian Community and entering Pinal County.
As of a 2006 estimate, the Broadway Curve portion of I‑10 in Tempe carries an average of 294,000 vehicles per day. This number is predicted to increase by over 150,000 to approximately 450,000 by the year 2025. This section of I‑10 is currently twelve lanes wide, and is the widest section of freeway in the valley. A study is underway to determine whether widening the Broadway Curve to double its current width to twenty-four lanes is feasible.