The first written mention about Žarnovica is dated to 1332.
Žarnovica lies at an altitude of 230 metres (755 ft) above sea level and covers an area of 30.4 square kilometres (11.7 sq mi). It is located in the Žiar Basin in central Slovakia, on the Hron River, between Vtáčnik and Štiavnické vrchy mountain ranges.
According to the 2001 census, the town had 6,596 inhabitants. 95.59% of inhabitants were Slovaks, 1.61% Roma and 0.73% Czechs. The religious make-up was 78.73% Roman Catholics, 15.25% people with no religious affiliation and 1.32% Lutherans.