St. Mary is a Roman Catholic church in Greenwich, Connecticut, United States, part of the Diocese of Bridgeport.

Around 1854, Greenwich became a mission station of St. John's in Stamford. Visiting priests offered Mass in private homes or at the Town Hall. In 1860 a small church was erected on William Street. The parish was founded in 1874.^[1] In 1875 Rev. M.A. Tierney added a choir gallery to the church. He later purchased land for a new church from James Elphich. During the tenure of Rev. Denis J. Cremin, the cornerstone of St. Mary's Church was laid by Bishop Thomas Galberry of Hartford.^[2] The new white frame colonial church was dedicated on May 18, 1879.^[1]

Rev. Thomas Smith became pastor in September 1879. He converted the old church on William St. into a school, which was staffed by the Sisters of Mercy from Middletown. The church was decorated in 1884 and enlarged in 1888.^[2] on May 16, 1900, a disastrous fire destroyed the early church along with a number of other buildings in the area.^[1]

The funeral of Adolphus W. Green, the founder of Nabisco (including Oreo biscuits), was held in this church on March 10, 1917.^[3]

Msgr. Frank Wissel was appointed pastor of St. Mary's in 1997. On the occasion of his retirement in 2014, a marble statue of Our Lady of the Miraculous Medal, donated anonymously, was erected outside the churchmin honor of Wissel. He died a week later on June 19 at the age of seventy-six.^[4]

The current stone church was designed in 1900 by Henry C. Pelton. The parish complex also contains a school and convent. St. Mary Church and Rectory are included as significant contributing properties in the Greenwich Avenue Historical District, Greenwich, Connecticut.^[5][6]