As most port areas throughout the world, Guanabara Bay (GB), which hosts the Harbour of Rio de Janeiro (HRJ), is under intense environmental stress. Located in one of the most iconic places of the world, GB environmental status has been the focus of worldwide attention with the imminent 2016 Olympic Games. The aim of this study was to discuss all past and current relevant aspects to characterize the environment of GB and its main harbour, including geomorphology, climatology, hydrology, geography and biodiversity aspects.