Propolis is a complex sticky material collected by a variety of bees including the honeybee. The honeybee uses it to coat the surfaces in the hive and block any holes in order to suppress any microbes in the hive. Propolis is a complex and its composition depends on the plants in the vicinity of the hive. In temperate regions it is mainly collected from poplar tree buds but in other regions, particularly the tropics, a variety of plants may be utilized. It has a range of biological properties including antimicrobial, anti-protozoal, antifungal, antiviral, anti-inflammatory, wound healing, anticancer, and antidiabetic properties. In addition, it has effects on cardiovascular health and also has an impact on bee health. Research on propolis is very active and there is a global interest in its potential for treating disease. Recently there has been a move to conduct double-blinded clinical trials using propolis in a variety of treatments. This chapter focuses largely on propolis studies conducted since the last edition of the book in 2017.