St. Mary's-By-The-Sea is a historic Gothic Revival church at 20 South Shore Road in Northeast Harbor, Maine. Designed by English architect Henry Vaughan and built in 1902, it is one of a number of architect-designed summer chapels built around the turn of the 20th century with funding from wealthy summer residents. The building was listed on the National Register of Historic Places in 2000. Its parish is also responsible for services at Saint Jude's Episcopal Church, another National Register-listed chapel in Seal Harbor.