Hay-a-Park Gravel Pit is a Site of Special Scientific Interest, or SSSI, adjacent to the east side of the town of Knaresborough, North Yorkshire, England. Having been a disused and flooded quarry since the 1970s, it now consists of the large Hay-a-Park Lake and three smaller ponds, besides associated reedbeds, scrub, woodland and grassland. It was designated as a SSSI in 1995 because it supports a number of wintering birds, including a large flock of goosander. This site is "one of the most northerly inland breeding populations of reed warbler in Britain." Hay-a-Park was once part of a royal park, an early landowner being Edward II.