Jáchymov, until 1945 known also by its German name of Sankt Joachimsthal or Joachimsthal (meaning "Saint Joachim's Valley") is a spa town in the Karlovy Vary Region of the Czech Republic. It has a population of about 2,500.

It is situated at an altitude of 733 m (2,405 ft) above sea level in the eponymous St. Joachim's valley in the Ore Mountains, close to the Czech border with Germany. The historical core of the town from the sixteenth century is today an urban monument zone. It is a comprehensive set of Gothic - Renaissance patrician houses.

The town has a long mining tradition; at first silver was mined here. In 1534, it was the second most populous town in the Kingdom of Bohemia. The silver Joachimsthaler coins minted there since the 16th century became known in German as Thaler for short, which via the Dutch daalder or daler is the etymological origin of the currency name "dollar". The Svornost mine (1525) is the oldest mine still in use in Europe, it is also the first and for a long time the only mine in the world where radium was mined.