The olive is a small evergreen tree native to Mediterranean regions, but naturalized to climates as varied as those of Australia, California, and Texas. The well-known green to blue-black fruit of this tree yields a useful, edible oil. Both the oil and the dried green-grayish colored leaves are used in herbal medicine. The reported benefits of olive leaf extract range from promoting increased energy and healthy blood pressure, to supporting the cardiovascular system and the immune system. Olive leaf extracts and their oleuropein constituents are best known for their blood pressure-lowering effects, but the latest studies reveal their health benefits extend well beyond that. Additional anti-inflammatory and antioxidant properties offer promise in fighting atherosclerosis, diabetes, cancer, neurodegenerative diseases, and even arthritis.