Otto I (also Otho or Ottone; died 991) was the second Marquis of Montferrat briefly following his father Aleram on the throne.
Notably obscure, he did not appear with his parents and his younger brother Anselm at the foundation of the monastery of Grazzano in 961.
On Aleram's death in 967, the large marca Aleramica was broken up: Montferrat went to Otto and Liguria to Anselm.
He appears in a confirmation of the possessions of the abbacy of Fruttuaria with the title in a patronymic.
He probably never used the title in life, but his descendants retroactively applied it to him, as he held the same post as they.