Dayu () is a county in the west of the prefecture-level city of Ganzhou, in the southwest of Jiangxi Province, bordering Guangdong Province to the south. It is known for The Capital of Tungsten.
Dayu has an area of . Total population is 280,000.
The county executive, legislature, judiciary are at Nan'an Town (Nanan) (), together with the CPC and PSB branches.
Dayu county is divided to 8 towns and 3 townships.