Karo Regency is a landlocked regency of North Sumatra Province of Indonesia, situated in the Barisan Mountains. The regency, which was established on 7 November 1956, covers an area of 2,127.25 square kilometres (821.34 sq mi) and according to the 2010 census it had a population of 350,479, increasing to 404,998 at the 2020 Census; the official estimate as at mid-2023 was 420,799, comprising 208,600 males and 212,200 females. 60.99% of the regency is forested. Its regency seat is the town of Kabanjahe. The Batak Karo language is spoken in the regency, as well as the Indonesian language. It borders Southeast Aceh Regency in Aceh to the west, Deli Serdang Regency and Langkat Regency to the north, Dairi Regency and Toba Samosir Regency to the south, and Deli Serdang Regency and Simalungun Regency to the east.

Deli Serdang is a regency in the Indonesian province of North Sumatra. It surrounds the city of Medan, and also borders to the west the city of Binjai, which is effectively a bedroom community for Medan. The entire regency lies within the Medan metropolitan area. It occupies an area of 2,241.68 km2. The capital of the district is Lubuk Pakam, which is located approximately 30 km east of Medan. The national census of 2000 recorded 1,573,987 people, but by 2010 the regency's population increased by 13.76% to 1,790,431, and at the 2020 Census the total was 1,931,441. The official estimate as at mid 2023 was 2,018,164. Kualanamu International Airport is located in this regency.