Marianus III, also Mariano d'Arborea, was the sole Judge of Arborea from at least 1310 to his death. He co-ruled with his elder brother Andreotto from the death of their father, John of Arborea, who left no legitimate heirs when he died sometime between 1304 and 1307.
- Occupation
- monarch
- Position held
- Judge of Arborea
- Citizenship
- Judicate of Arborea
- Born
- 1250
- Died
- 1321
