Diocesan Classical Gymnasium "Ruđer Bošković" (Croatian: Biskupijska klasična gimnazija Ruđera Boškovića u Dubrovniku) is a classical gymnasium in Dubrovnik, Croatia. It is affiliated with and operated by the Roman Catholic Diocese of Dubrovnik. It is named after former student Ruđer Bošković.

It is one of the city's oldest educational institutions with roots dating back to a seminary founded by the Jesuits during the 17th century. The Collegium Ragusinum was the first such institution in the city of Dubrovnik. It had a strong tradition in the maritime sciences and is the predecessor of the present-day University of Dubrovnik. In 1941 the secondary school section was founded.

The Diocesan Classical Gymnasium is not to be confused with Gimnazija Dubrovnik, which is a state-funded (rather than church-affiliated) general gymnasium outside the old town.

In 1941, the classical gymnasium was formally established as a secondary school, continuing the legacy of its educational roots while expanding its focus to a broader classical curriculum. Today, it is known for its academic rigor and religious affiliation, nurturing students in both intellectual and spiritual development.

The Diocesan Classical Gymnasium "Ruđer Bošković" is distinct from other educational institutions in Dubrovnik, particularly the Gimnazija Dubrovnik, which is a state-funded, non-religious general gymnasium located outside the old city walls. The Diocesan Classical Gymnasium, on the other hand, remains closely tied to the Catholic Church and continues its tradition of providing a faith-based education with a focus on classical studies.

As one of Dubrovnik’s most prestigious schools, the Diocesan Classical Gymnasium has produced many notable alumni who have contributed significantly to various fields, including the sciences, arts, and the Church. The school continues to attract students who are interested in pursuing a rigorous classical education while maintaining its strong ties to the city's historical and cultural heritage.

42°38′21″N 18°06′33″E / 42.6393°N 18.1093°E / 42.6393; 18.1093