The last Finnish-born bishop was Arvid Kurki, who died in 1522.
Sippo has served as Diocesan administrator since last summer, when the previous bishop, Józef Wróbel, was sent back to his native Poland to serve as an auxiliary bishop.
Pope Benedictus XVI appointed Sippo to the post in June.
Finland is home to only some 10,000 Catholics. The whole country forms one single diocese.