The Jerónimos Monastery or Hieronymites Monastery is a former monastery of the Order of Saint Jerome near the Tagus river in the parish of Belém, in the Lisbon Municipality, Portugal. It became the necropolis of the Portuguese royal dynasty of Aviz in the 16th century but was secularized on 28 December 1833 by state decree and its ownership transferred to the charitable institution, Real Casa Pia de Lisboa.