Are reef sharks replaceable? Or do they perform ecological functions that other predators cannot? This talk tackles that question by synthesizing evidence from feeding mechanics, trophic ecology, prey demography, fear effects, and cross-habitat coupling. Although mesopredatory reef sharks often overlap with large teleost predators in diet, they differ fundamentally in morphology, attack mode, movement behaviour, and the spatial scale at which they influence ecosystems. These differences matter. They shape prey-size ranges, foraging tactics, links between reef and pelagic habitats, and the extent to which predators generate broad seascapes of risk. I argue that the long-running debate over whether sharks “matter” has often been obscured by mismatches in spatial and temporal grain, predator movement scales, and multi-predator context. Building on recent frameworks, I organize the evidence around three pathways, consumptive, risk, and coupling, and show how these can be used to distinguish substitutability, buffering through response diversity within sharks, and true ecological uniqueness. My conclusion is that sharks may sometimes be substitutable for local consumptive effects, but they are far less easily replaced in cross-habitat coupling and wide-ranging risk effects. Resolving where, when, and how sharks matter most remains central to understanding coral reef resilience.