The Tiara of Pope John XXIII was the personal Papal Tiara (triregnum in Latin, triregno in Italian) presented by the region of Bergamo to Angelo Roncalli, who was born there, following his election as Pope John XXIII in 1958.

Because Pope John's election as pope was so unexpected the region had not made plans to have a tiara manufactured. As a result John was crowned with the 1877 Palatine Tiara given to Pope Pius IX. In 1959 the tiara was completed and given to the Pope in the Vatican.

When asked for guidance as to its design, Pope John requested that it be lightweight and that the number of jewels the region was planning to use be halved, with the savings donated to the poor. The tiara as a result is the joint-lightest in papal tiara collection, weighing only 2 lbs (900g)

John wore the tiara regularly during his papacy when not wearing either the Palatine Tiara or the Tiara of Pope Pius XI.

It has remained unworn since his death in 1963. His successor Pope Paul VI was supplied with his own, far heavier solid silver tiara. Pope Paul later dispensed with wearing any tiara. Later popes, though they never abolished the wearing of the tiara, have chosen personally in each case not to wear one. However it remains open to any future pope to wear any of the tiaras in the Vatican's possession, including the Tiara of John XXIII.