St. Mary’s Church, Belfast, a Roman Catholic church located in Chapel Lane/Smithfield area of Belfast, Northern Ireland, opens for public worship on May 30, 1784. It is mother church for the city. At the time, it is the only Roman Catholic church in the then town of Belfast after the relaxation of some of the Penal Laws. The church grounds contain an undistinguished grotto dedicated to Our Lady of Lourdes.

In the census of 1782, there are only 365 Catholics recorded living in Belfast. Following a collection from the local Church of Ireland and Presbyterian congregations, funds are donated to the building of St. Mary’s Church.

The first Mass is celebrated on Sunday, May 30, 1784, by Father Hugh O’Donnell, the first Parish Priest of Belfast. In the opening ceremony, a company of the Irish Volunteers line the chapel yard and escort Father O’Donnell into the building.

In 1813, the church’s pulpit is donated by the Anglican Vicar of Belfast, Canon Turner, continuing the positive relationship between the Roman Catholic church and the local Protestant congregations. Later, in 1815, St. Patrick’s Church is built to accommodate the growing Catholic population of the city.

As Belfast’s Catholic population grows after the famine, the church is deemed too small and thus architect John O’Neill is contracted to design a church big enough for the burgeoning congregation. Although none of the original church can be seen, in 1868 the church is enlarged and renovated into a new Romanesque style building.

In the Marian Year of 1954 a Grotto to Our Lady of Lourdes is established under the auspices of the then Administrator, Fr. Bernard MacLaverty, an uncle of the Belfast novelist of the same name. The grotto is created in the gardens surrounding the church by the Belfast architect Padraic Gregory.

To mark the bicentenary the sanctuary is renovated in 1983 with work by artist Roy Carroll, a favourite of Cahal Daly. Much of this timber furniture is later removed after Daly’s departure from the Diocese of Down and Connor.

In May–August 2017, the church undergoes substantial renovation work to repair the roof and walls, and to repave the grotto area.

For almost forty years the church is served by clergy from the Mill Hill Fathers, the last of whom leave in 2019. The current Administrator is Fr. Timothy Bartlett assisted by a range of retired clergy. The church holds two masses a day on Sunday and Monday, and three a day on Friday and Saturday. The 6:00 p.m. Mass on both Friday and Saturday are held in the Irish language.