Two barrier island systems from southern Mozambique (Inhaca and Bazaruto) are described. Both systems comprise a composite barrier island or barrier island chain that developed on a steep continental margin as a result of initial (Pleistocene) spit progradation. Continuing aeolian dune deposition against this initial core during subsequent sea-level highstands and lowstands has given rise to the highest dunes (120m) of any known barrier island. Wave reworking of the composite barrier island sediment during the past 6000 years of the Holocene sea-level highstand has resulted in the formation of spits, barriers, barrier islands and bluffs on the downdrift and bay side sections of the barrier island systems. The relative stability in position of the barrier systems at contemporary sea level is attributed to their large sediment volume and the development of equilibrium shoreline forms under swell waves. Beachrock and aeolianite outcrops provide anchor points for the development of contemporary shoreline forms.