Hasištejn () is a ruined medieval castle in Bohemia, the Czech Republic. It is situated near Kadaň, Klášterec nad Ohří and Chomutov. The castle, first mentioned in Maiestas Carolina, was probably founded by Friedrich of Schönburg to guard the way from Prague to Saxony. The castle was seized by Václav IV of Luxembourg and it was given to the house of Lobkovic.