Castle of Castelnuovo Magra, Medieval castle in Castelnuovo Magra, Italy.

The Castle of Castelnuovo Magra is the episcopal palace-fortress of Luni, standing on Piazza Querciola in the historic centre of Castelnuovo Magra, in the Magra valley. Begun at the end of the 13th century for Bishop Enrico da Fucecchio, it preserves a quadrangular tower with sandstone corbels added in 1468 and a circular tower built by the Republic of Genoa in the 16th century as a munitions store, plus stretches of the perimeter walls.

A defensive post existed at the Borghetto by the early 13th century, built under Bishop Gualtiero II when the town was founded. At the end of that century Bishop Enrico da Fucecchio had the present bishop's palace and diocesan seat built. In the first half of the 15th century the Medici restored the square tower, adding sandstone corbels in 1468; in the 16th century Genoa built the round tower as a munitions store.

The castle stands in Piazza Querciola, in the historic centre of Castelnuovo Magra. Each summer the square in front of it hosts a re-enactment of the 1306 Peace of Castelnuovo, the agreement linked to Dante Alighieri, who stayed in the town as envoy of the Malaspina family.

The site functions as a cultural center and regularly hosts municipal and cultural events that make it accessible to the public. Visitors should check in advance what activities are happening during their visit, as the site's use varies by season.

The castle's stones were quarried away over centuries for local houses; the last authorised removal, in the 19th century, supplied the choir of the parish church of Santa Maria Maddalena. Only the two towers, one round and one square, and stretches of the perimeter walls survive of the medieval palace.