Ngawi Regency is an inland regency (kabupaten) of Indonesia, on the island of Java. Ngawi is well known around the world for its Pithecantropus erectus which was found by Eugene Dubois, a Dutchman. Ngawi is located in East Java Province but adjoins Central Java province. Its capital Ngawi (city). Ngawi is also the main gate to enter East Java province since there are intersections that connect Surabaya–Bojonegoro–Ngawi (city)–Solo–Jogja–Bandung–Jakarta. The Regency covers an area of 1,394.74 km2 (538.51 sq mi), and had a population of 817,765 at the 2010 census and 870,057 at the 2020 census; the official estimate as of mid-2023 was 904,094.

East Java is a province of Indonesia located in the easternmost third of Java island. It has a land border only with the province of Central Java to the west; the Java Sea and the Indian Ocean border its northern and southern coasts, respectively, while the narrow Bali Strait to the east separates Java from Bali by around 2.29 kilometres (1.42 mi). Located in eastern Java, the province also includes the island of Madura, as well as the Kangean islands and other smaller island groups located further east and Masalembu archipelagos in the north. Its capital is Surabaya, the second largest city in Indonesia, a major industrial center and also a major business center. Banyuwangi is the largest regency in East Java and the largest on the island of Java.