Mastalus II (Italian : Mastalo) (died 958) was the first duke of Amalfi from 957 until his death.
He succeeded his father as patricius in 953, when he was still a minor. He came of age in 957 and was elected dux , raising him to equal rank with the Dukes of Gaeta and Naples. In the next year, he was assassinated by Sergius of Musco Comite family on the Monte di Scala.