The Basilica of the National Shrine of the Immaculate Conception is a Catholic minor basilica and national shrine in Washington D.C.. It is the largest Catholic church building in North America and is also the tallest habitable building in Washington, D.C. Its construction of Byzantine and Romanesque Revival architecture began on 23 September 1920.

Basilicas are Catholic church buildings that have a designation, conferring special privileges, given by the Pope. Basilicas are distinguished for ceremonial purposes from other churches. The building need not be a basilica in the architectural sense. Basilicas are either major basilicas, of which there are four, all in the Diocese of Rome, or minor basilicas, of which there were 1,810 worldwide as of 2019.