Icklesham's historic roots can be traced back to 772, when it appeared as Icoleshamme in a land charter signed by Offa, King of Mercia. Strategically located on the River Brede, it was a prime target in the Norman invasion of 1066 (some 700 years later, evacuation plans were prepared in case of an invasion by Napoleon). The 12th-century parish church is dedicated to St Nicholas.
The parish contains three Sites of Special Scientific Interest—Winchelsea Cutting, "Dungeness, Romney Marsh and Rye Bay" and Rye Harbour. Winchelsea Cutting is a 0.3 acres (0.12 ha) roadside cutting with 33 feet (10 m) of exposed geological strata. Dungeness, Romney Marsh and Rye is a large site of 1,801 acres (728.8 ha), laying along the coast, and extending into the neighbouring county of Kent. Its interest is biological and geological, with various habitats of shingle, saltmarsh, sand dunes and saline lagoons. Rye Harbour is another 1,881 acres (761.2 ha) site of biological importance, with a varied habitat of shingle, intertidal mudflats and saltmarsh.