Sidoarjo Regency is a regency located in East Java, Indonesia. It serves as a significant administrative division situated south of the city of Surabaya. The regency's capital is located within the Sidoarjo District.
Covering an area of approximately 719.34 km2, Sidoarjo is the geographically smallest regency in the province of East Java. Despite its small size, it is densely populated, with an estimated population of 2,027,874 residents as of mid-2024.
The region is an integral part of the Gerbangkertosusila metropolitan area. It shares borders with several other major areas, including Surabaya, Gresik, Pasuruan, Mojokerto, and the Madura Strait.