45 prior to 1999[1]) is a Catholic school board located in Durham Region, east of Toronto, Ontario.

The DCDSB has engaged in a focused effort to improve student learning through ongoing staff development in the area of instructional leadership.

Of note is the steady improvement in student achievement as reported by the results of Provincial Assessments in math and literacy, also known as the EQAO tests.

[citation needed] The DCDSB was previously known as the Durham Region Roman Catholic Separate School Board (DRRCSSB) until the end of 1997, operating both anglophone and francophone schools.

The French schools in the Durham Region are now operated by Conseil scolaire catholique MonAvenir.