Alumina (Al2O3) ceramic is widely used for medical devices and its biocompatibility is well known and is reported in articles and textbooks. However, finding proof of this assertion gathered over more than 40 years can be challenging. We performed a literature review about alumina biocompatibility to compile data from the literature. We searched for articles on the biocompatibility of alumina in relation to the ISO 10993-1 International Standard, which defines the biocompatibility of biomaterials. For every biological effect listed in the norm, such as cytotoxicity, sensitization, implantation, and genotoxicity, in vitro and in vivo tests in animals and humans did not reveal any abnormal biological response. Proof for the the well-known biocompatibility of alumina is summarized in this review.