Diocese of Šiauliai (Latin: Dioecesis Siauliensis) is a Roman Catholic Diocese of Lithuania. The current bishop is Eugenijus Bartulis (since 1997). The diocese in present structure and territory was established on May 27, 1997.

The diocese covers an area of 7,696 km (2,971 sq mi), and is a suffragate of the Archdiocese of Kaunas. In 2004 the diocese of Šiauliai had about 269,861 believers (79.7% of the population), 65 priests and 67 parishes.

The Cathedral of Saints Peter and Paul in Šiauliai has been assigned as the Cathedral of the diocese. The main pilgrimage place is Hill of Crosses.