Aceh Tamiang Regency () is a regency in the east of Aceh province of Indonesia, bordering on North Sumatra Province to the east. It is located on the island of Sumatra, and was formed on 10 April 2002 from what were previously the southeastern districts of East Aceh Regency. The regency covers an area of 1,957.02 square kilometres and had a population of 251,914 people at the 2010 census, 277,766 at the 2015 census and 294,356 at the 2020 Census; the official estimate as of mid 2024 was 312,061 - comprising 157,740 males and 154,321 females. It is bordered to the east by the Langkat Regency of North Sumatra Province, by Gayo Lues and East Aceh Regencies and the city of Langsa to the west, and by the Malacca Strait to the north. The seat of the regency government is at the town of Karang Baru.
The regency is divided administratively into twelve districts (kecamatan), listed 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 location of the district administrative centres, the number of villages (gampong) in each district, and its postal code.