The Algoa Bay Sentinel Site is a coastal observatory comprising four programmes and a geographical footprint spanning >300 km of coastline on the warm-temperate south-east coast of South Africa. The Continuous Monitoring Programme (CMP) comprise 37 permanently moored in situ observatories measuring a series of physical properties of the coastal ocean between Port Alfred and Oyster Bay. The Pelagic Ecosystem LTER Programme (PELTER) perform long-term observations selected Essential Biodiversity Variables (EBV), including phytoplankton and zooplankton. The Sandy Beaches LTER Programme (SBLTER) entail observations of short- and long-term changes in surfzone diatoms among other variables at 10 sandy beach stations in Algoa Bay. The Rocky Shores LTER Programme (RSLTER) conducts repeat observations of benthic communities associated with 7 stations on Algoa Bay island complexes and surrounding shores. The Benthic Ecosystem LTER Programme employs remote imagery technologies (sBRUV, ROV, jump cameras) to monitor long-term change in the community structure of fishes and invertebrates. First observations commenced in 2008 and is ongoing. In situ moorings record water temperature and current velocity at hourly intervals and are serviced every 3 to 6 months. PELTER and SBLTER stations are sampled monthly, while BELTER and RSLTER stations are visited quarterly and biannually respectively. The majority of moorings and stations are situated within the Addo Elephant National Park Marine Protected Area, home to the largest remaining African Penguin colony in the world. ABSS data serve conservation, research and resource management efforts.