Marianus III of Arborea

Marianus III (died 1321) was Judge of Arborea, an illegitimate son of Judge John and Vera Cappai. He co-ruled with his elder brother Andreotto from 1304, ruling alone from about 1310. In 1312 Pisa forced him to buy his succession rights from the Emperor Henry VII and to marry Constance of Montalcino by proxy; he never did, and lived instead with Padulesa de Serra, who bore him six children, including his successor Hugh II.

In 1314 he sought Aragonese aid against Pisa. He restored roads and bridges and completed the walls and towers of Oristano.