| St. Mary's Church | |
| Pushpin Map: | United Kingdom County Durham |
| Pushpin Label Position: | right |
| Pushpin Mapsize: | 240 |
| Map Caption: | St. Mary's Church shown within County Durham |
| Coordinates: | 54.542°N -1.409°W |
| Osgraw: | NZ383165 |
| Location: | Longnewton, Stockton-on-Tees |
| Country: | England |
| Denomination: | Anglican |
| Dedication: | Blessed Virgin Mary |
| Consecrated Date: | Pre 1806 |
| Status: | Parish church |
| Functional Status: | Active |
| Diocese: | Durham |
| Curate: | Susannah Green |
| Minister: | John Lambert (Associate) |
| Reader: | John Taylor |
St. Mary's Church, Longnewton is a Church of England church in the parish of Longnewton, Stockton-on-Tees, Teesside, England. It is part of the benefice of All Saints' Church, Preston-on-Tees.
It is a small stone building in the Early English style, twice rebuilt, in 1806 and in 1858, and occupying the site of a more ancient church.
There is a nave, chancel, and south aisle; north of the chancel, forming a transept, is the Londonderry mausoleum, within which is a sculptured white marble tomb of the third Marquis of Londonderry. The present building is Grade II* listed.
There was formerly a chantry in this church, dedicated to the Blessed Virgin Mary.
The church has links with St. Mary's Church of England Aided Primary School in Longnewton.