Port Stephens, an open youthful tide dominated drowned valley estuary, is a large natural harbour of approximately 134 square kilometres (52 sq mi) located in the Hunter Region of New South Wales, Australia. Port Stephens lies within the Port Stephens-Great Lakes Marine Park and is situated about 160 kilometres (99 mi) north-east of Sydney. The harbour lies wholly within the local government area of Port Stephens; although its northern shoreline forms the boundary between the Port Stephens and Great Lakes local government areas. According to the 2006 Census, more than 26,000 people lived within 3 km (1.9 mi) of its 113 km (70 mi) long shoreline and more than 32,000 lived within 10 km (6 mi).
Port Stephens is formed through the confluence of the Myall and Karuah rivers, Tilligerry Creek, and the Tasman Sea of the South Pacific Ocean. The lower port has a predominantly marine ecology and the upper port an estuarine ecology. The area to the east of Port Stephens comprises the Tomago/Tomaree/Stockton sand beds. A narrow entrance between two striking hills of volcanic origin marks the opening of Port Stephens to the sea. The southern headland, Tomaree or South Head, rises to 120 metres (390 ft) above mean sea level (AMSL) while Yacaaba, the northern headland, is 210 m (690 ft) AMSL. The harbour is mostly shallow and sandy but contains sufficient deep water to accommodate large vessels. After its recovery from the wreck site in 1974 the bow of the MV Sygna, a 53,000 tonnes (52,163 long tons) Norwegian bulk carrier that was shipwrecked on Stockton Beach earlier that year, was moored in Port Stephens, at Salamander Bay, for almost two years. With an area of approximately 134 square kilometres (52 sq mi), Port Stephens is larger than Sydney Harbour. Port Stephens extends approximately 24 km (15 mi) inland from the Tasman Sea and at its widest point, between Tanilba Bay and Tahlee, it is 6.5 km (4 mi) across. The narrowest point is between Soldiers Point and Pindimar where the distance is only 1.1 km (0.7 mi). Between Nelson Bay and Tea Gardens, in the most well known section of the port, it is 3.8 km (2.4 mi) wide. The Karuah River drains into Port Stephens at its north-western corner. The Myall River (through the Myall Lakes) drains into the port on its northern shore, about 5.7 km (3.5 mi) from the mouth of the port. Twelve Mile Creek drains into the port’s south-western corner.
Looking towards the mouth of Port Stephens along Jimmys Beach from Winda Woppa. The southern shore of the port is divided into two distinct areas known as the Tomaree and Tilligerry peninsulas. These are separated by Tilligerry Creek, a watercourse covering approximately 7.7 km2 (3.0 sq mi), which drains the land in the low-lying areas of Salt Ash, Bobs Farm, Tanilba Bay and Mallabula. While the Tilligerry Peninsula is geographically closer to major centres such as Sydney and Newcastle, it lacks the urban development that has occurred on the much larger (25 km2 (10 sq mi) vs 115 km2 (44 sq mi) respectively) Tomaree peninsula. Although Lemon Tree Passage, on the Tilligerry Peninsula, and Soldiers Point, on the Tomaree Peninsula, are only 2.9 km (1.8 mi) from each other, physical separation of the suburbs by Port Stephens and Tilligerry Creek results in them being almost 40 km (25 mi) from each other by road. The town of Karuah, located at the north-western corner of the port near the mouth of the Karuah River, experiences similar geographical separation from the Tilligerry Peninsula. Despite being only 7.7 km (4.8 mi) from Tanilba Bay, the road distance between the two suburbs is 40 km (25 mi). The western shore and the western part of the northern shore of the port are largely undeveloped with the flora ranging from scrubland in the west to the large tracts of bushland which are present along most of the northern shore. Closer to the mouth of the port, at and near Winda Woppa, sandy beaches are prevalent. These extend from Jimmys Beach, near the mouth of the port, to the mouth of the Myall River, a distance of approximately 5.2 km (3.2 mi). Just outside the mouth of the port lie the two small insular nature reserves of Cabbage Tree Island and Boondelbah Island, both dedicated to the conservation of the threatened Gould’s petrel, and with no public access.