|Archipelago||Tlukerian Islands, Shaelic Sea|
|Autonomous Province||Tlukera and Deyatsan|
|Largest settlement||Ach (pop. 8,538)|
|Ethnic groups||Deyatsa, Tlukerians, Fazul, others|
Deyatsan (Deyatsa Teyetsen /tajat͡san/, Faźul: Delyazan /dejɑt͡sɑn/), is the second-largest and westernmost of the Tlukerian Islands, an island chain located in the Shaelic Sea. It is home to about 14,000 people—about 7% of the population of the Fazul province of Tlukera and Deyatsan. Its largest settlement, Ach, is located on its southeastern coast.