The Arno River floods Florence, Italy, to a maximum depth of 6.7 m (22 ft), leaving thousands homeless and destroying millions of masterpieces of art and rare books. Venice is also submerged on the same day at its record all-time acqua alta of 194 cm (76 in).

The Arno is a river in the Tuscany region of Italy. It is the most important river of central Italy after the Tiber.

The 1966 flood of the Arno in Florence killed 101 people and damaged or destroyed millions of masterpieces of art and rare books. It is considered the worst flood in the city's history since 1557. With the combined effort of Italian and foreign volunteers alike, or angeli del fango, many of these fine works have been restored. New methods in conservation were devised and restoration laboratories established. However, even decades later, much work remains to be done.

Florence is the capital city of the Italian region of Tuscany. It is also the most populated city in Tuscany, with 362,353 inhabitants, and 989,460 in its metropolitan province as of 2025.

The 1966 Venice flood was an unprecedented high water, known in Venice as an "acqua alta", with waters reaching up to 194 cm.

An acqua alta is an exceptional tide peak that occurs periodically in the northern Adriatic Sea. The term is applied to such tides in the Italian region of Veneto. The peaks reach their maximum in the Venetian Lagoon, where they cause partial flooding of Venice and Chioggia; flooding also occurs elsewhere around the northern Adriatic, for instance at Grado and Trieste, but much less often and to a lesser degree.