The French archipelago of New Caledonia hosts one of the three most extensive reef systems in the world and was partly added to the UNESCO World Heritage List in 2008. In the very specific context of rapidly growing land-based mining extraction and ore processing activities, industrial managers, political decision makers, lagoon users and citizens have been expressing an increasing demand for the implementation of efficient environmental monitoring programs dedicated to the effects related to mining activities. As a result, New Caledonia lagoons were thoroughly studied particularly during the last two decades through national research projects. This chapter aims at reviewing the state-of-the-art of knowledge about the general features of New Caledonia geography and climatology, lagoon environmental drivers including hydrodynamics, pelagic and benthic processes, and the potential stress of terrestrial and anthropogenic inputs on marine communities. Insights addressing economic, ecological and political issues related to the complex status of self-governed New Caledonia are discussed with respect to living resources and environmental management.