The Łęczyca Royal Castle is a medieval castle situated in Łęczyca, Poland. The castle was erected by Casimir III the Great as a fortification during 1357–1370.
Immediately after its completion, the Castle became a residence of king Casimir the Great, and then was the seat of the governor of Łęczyca. In 1406 it was burned by the Teutonic Knights and rebuilt in the following years to serve as a place of a conference in 1409, where decisions were taken in connection with the approaching war with the Order. After the Battle of Grunwald many of the Teutonic Knights were incarcerated here. In subsequent years, four diets were held here (1420, 1448, 1454 and 1462), and the castle became the seat of the king Casimir IV Jagiellon during another war with the Order (1454-1466).
After a great fire in the second half of the 15th century the castle remained in ruins till the early 1560s. Then, in 1563