Alexander Bay (Afrikaans: Alexanderbaai) is a town in the extreme north-west of South Africa, also known as the region of Little Namaqualand. It is located on the southern bank of the Orange River mouth. It was named for Sir James Alexander, who was the first person to map the area whilst on a Royal Geographical Society expedition into Namibia in 1836. (It is mistakenly believed by many locals that it was he who first established commercial copper mining in the area.) With diamonds being discovered along the West Coast in 1925, Alexander Bay was established to service the mining industry.
The town of Oranjemund lies on the northern bank of the river, which forms the international border with Namibia. The two towns are linked by the Harry Oppenheimer Bridge, named for Harry Oppenheimer in 1951.
The town is served by an airport known as the Alexander Bay Airport.