St Mary's College is a year 7–13 integrated Catholic girls' high school situated at 11 New Street, Ponsonby, Auckland in New Zealand.

It was established in 1850 on the site of the present St Patrick's Cathedral, in Wyndham Street by the Sisters of Mercy, who were founded in Ireland by Catherine McAuley in 1831.

A large new convent was built in Ponsonby, overlooking the Waitemata Harbour and the central business district of Auckland City and the school was shifted there in 1861.

During the 20th Century, under the direction of the late Dame Sister Mary Leo, the school produced many singers of international fame, notably Dame Kiri Te Kanawa and Mina Foley.

The college is still owned by the Sisters of Mercy who have established a board of directors which works in conjunction with the board of trustees to ensure that the Catholic character of the school is not only maintained but enhanced and promoted.