Lago di Bientina, also known as Lago di Sesto, was a lake in Tuscany, Italy. Located to the north of the town of Bientina, between Lucca and Pisa, the lake was historically subject to numerous efforts at drainage due to its tendency to flood. Early attempts at canal-building and drainage in the 16th century were hampered by the lake's connection with the Arno River, which often led to backflow and even increased flooding.

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