Crown jewels are the objects of metalwork and jewellery in the regalia of a current or former monarchy. They are often used for the coronation of a monarch and a few other ceremonial occasions. A monarch may often be shown wearing them in portraits, as they symbolize the power and continuity of the monarchy. Additions to them may be made, but since medieval times the existing items are typically passed down unchanged as they symbolize the continuity of the monarchy.

Typical items in Europe include crowns, sceptres, orbs, swords, ceremonial maces, and rings, all usually in gold or silver-gilt and heavily decorated with precious and semi-precious gemstones, in styles which go back to the Middle Ages and are normally very conservative to emphasize the continuity of the monarchy. Many working collections of crown jewels are kept in vaults or strongrooms when not in use and can be seen by the public. The crown jewels of many former monarchies can also be seen in museums, and may still represent national cultural icons even for countries that are now republics, as for example in Hungary, where the Holy Crown of Hungary has been re-incorporated in the coat of arms of Hungary. Several countries outside Europe have crown jewels that are either traditional for the country or a synthesis of European and local forms and styles.