The Roman Catholic Diocese of Rockville Centre comprises the territory of
Nassau and
Suffolk counties (regionally known as
Long Island) in
New York state,
USA. Founded in 1957, this diocese was created from territory that once belonged to the
Diocese of Brooklyn. It is the sixth-largest Catholic diocese in the United States, currently serving approximately 1.5 million people in 134 parishes. The diocese is named for the village where its
cathedral,
St. Agnes Cathedral, is located,
Rockville Centre in Nassau County.