St. Mark's Episcopal Church is a historic Episcopal church at 69-75 Hudson Avenue in Green Island, Albany County, New York. It was built in 1866–1867 in a Gothic Revival style. It is a rectangular, brick trimmed stone church building with a steeply pitched roof with three steeply pitched dormers, covered in polychrome slate. The front gable features three pointed Gothic windows and a rose window. It also has a stone bell tower. The two story brick rectory was added in 1883–1884. It was listed on the National Register of Historic Places in 1978.