William III was the third Marquis of Montferrat and Count of Vado from 991 to his death. He was the eldest son and successor of Otto I. William I and II were the father and son, respectively, of Aleram, the first Marquis, but neither served as Marquis himself.
- Occupation
- sovereign
- Position held
- marquis of Montferrat
- Born
- 970
- Died
- 1042
