We describe the mating behavior of free-ranging Blacktip Reef Sharks, Carcharhinus melanopterus, at Palmyra Atoll. This is the first primary report of mating in C. melanopterus and the first direct observation of mating for an obligate swimming shark species. Similar to mat in other nonobligate swimming shark species, mating in C. melanopterus was characterized by multiple males following a single female, a male grabbing the female near the pectoral fin and positioning her head down on the bottom, and the insertion of a single clasper. Copulation lasted 68 sec, which is shorter than the durations recorded for most other shark species.