Loss of dispersal ability “behavioural flightlessness” is one of the defining characteristics of island biotas. Strong selection against dispersal should favour individuals with behaviour, navigational and sensory processes that reinforce site-fidelity. Here we evaluated if, and by what means, the Komodo dragon (Varanus komodoensis) the world’s largest lizard achieved restricted dispersal. Using extensive mark-recapture, telemetry, and experimental translocations indicated that direct selection has constrained dispersal in Komodo dragons. Despite impressive physical and sensory capabilities, this species almost always limited movement to within resident valleys indicating near complete dispersal restriction. Moreover stringent site fidelity was reinforced by lizards being hydrophobic and insensitive to several basic drivers of dispersal evolution (e.g. inbreeding avoidance) that otherwise reduced survival. Our results suggest that restricted dispersal is an extreme response to dispersal costs; and thus whilst promoting locally adapted populations common to archipelagoes, highlights how rapid global change will further challenge dispersal restricted island endemics.