Palinurid (spiny) lobsters are a group of highly mobile decapod crustaceans (Childress and Jury 2006). An understanding of lobster behaviour and habitat use is valuable for fisheries management and conservation, especially since palinurids are among the world’s most sought-after seafood. The painted spiny lobster (Panulirus versicolor) exclusively inhabits coral reefs of the Indian and Pacific Oceans, including the Great Barrier Reef (GBR; Australia). Although some lobster species show fidelity to small reef areas, none are known to remain in the same place for periods up to a decade (Childress and Jury 2006). Here we report an observation of long-term (decadal) site fidelity of P. versicolor from Northwest Island (23°18’S, 151°43’E) in the GBR. On 3 May 2013, we captured a male P. versicolor (144 mm carapace length) that was initially captured on 28 December 2003 (114 mm carapace length). Identity was confirmed via elastomer implant and unique body markings (Fig. 1). Initial capture and final capture occurred at the same coral shelter or den (confirmed by GPS), although it was known occasionally to use other nearby dens (within 200 m). It shared a den with a small (two to three) harem of females, which changed through time. Despite being periodically harassed (i.e. captured and handled on at least five occasions between 2004 and 2006) and occasionally injured (i.e. limb loss due to autotomy), this individual maintained a long-term association with a particular den. Previous work has shown that individual spiny lobsters, including those of Jasus edwardsii and P. versicolor, are capable of moving 0.5–6 km (Kelly and MacDiarmid 2003; Frisch 2007). A high degree of site fidelity in marine species is often associated with a tendency towards over-exploitation and/or vulnerability to extinction (Cheung et al. 2007). Given the importance of the den for protection against potential predators and for providing mating opportunities, it is likely that protection of high quality dens (in marine reserves, for example) may provide excellent conservation outcomes for this species.