Consumption of olive oil within the Mediterranean diet has been long known to have many health benefits. However, only over the last decade has epidemiological research confirmed its protective role against developing several chronic diseases. The objective of this review was to give an overview of the state of art epidemiological evidence concerning the relationship between olive oil and key public health outcomes including mortality, CVD, diabetes, metabolic syndrome (MetS), obesity and cancer, with a particular focus on recent results from cohort studies and dietary intervention trials. Recent epidemiological research has shown that regular consumption of olive oil is associated with increased longevity. This benefit is partly due to the olive oil's unequivocal cardio-protective role. There is converging evidence on the benefits of olive oil for preventing several CVD risk factors, including diabetes, MetS and obesity. Olive oil is also implicated in preventing certain cancers, with the most promising findings for breast and digestive tract cancers, although the data are still not entirely consistent and mainly from case-control studies. These health benefits are supported by strong mechanistic evidence from experimental studies, demonstrating that specific components of olive oil have antihypertensive, antithrombotic, antioxidant, antiinflammatory and anticarcinogenic action. Despite the accumulating epidemiological research, there is still a lack of consistent results from high-quality studies for many health outcomes (i.e. certain cancers and metabolism-related disorders). Further research is mandatory, above all from prospective studies and randomised dietary intervention trials when feasible, to confirm some of the still potential health benefits.