Rembang Regency (Indonesian: Kabupaten Rembang) is a regency (Indonesian: kabupaten) on the extreme northeast coast of Central Java Province, on the island of Java (bordering on the Java Sea) in Indonesia. The regency covers an area of 1,036.70 km² on Java, and it had a population of 591,359 at the 2010 Census and 645,333 at the 2020 Census; the official estimate as of mid-2023 was 665,237 (of whom 334,305 were males and 330,932 were females). Its administrative capital is the town of Rembang.

It is a lowland, with a maximum elevation of about 70 metres (230 ft) above sea level.

The Solo River flows through its inland section.

The regency is crossed by the North Coast Road, an inter-province main road on the island.

Rembang Regency is bordered by:

The regency is divided into fourteen districts (kecamatan), tabulated below with their areas and their populations at the 2010 Census and the 2020 Census, together with the official estimates as of mid-2024. The table also includes the locations of the district administrative centres, the number of administrative villages in each district (totaling 287 rural desa and 7 urban kelurahan - the latter all in Rembang town District), and its post-code.

Note: (a) Rembang (town) District comprises 7 urban kelurahan (Gegunung Kulon, Kutoharjo, Leteh, Magersari, Pacar, Sidowayah and Tanjungsari) and 27 rural desa.

Rembang has a tropical monsoon climate (Am) with moderate to little rainfall from May to October and heavy rainfall from November to April.