Bioadhesion is a versatile tool used by many organisms for a variety of purposes. It has roles to play in construction, predation, defense, and attachment and covers different concepts based on biochemical and mechanical principles. The specific request on the bond combined with millions of years of evolution results in diverse inspirations for medical and technical applications. This requires knowledge of the adhesives themselves in terms of composition, structural design, and interaction with surfaces. This chapter gives an overview about natural adhesives and biological adhesives leading to bioinspired applications. The terminology used in this chapter is based on the adhesive's origin and usage and the underlying concept: while natural adhesives are composed of bio-based raw materials for artificial applications, biological adhesives are expressed by natural organisms for versatile purposes. The latter in particular can lead to bioinspired applications that are not restricted to adhesion, including concepts to avoid adhesion as in terms of antifouling. Both kinds of adhesive, i.e., natural and biological, are relevant for biocompatible adhesives. This characteristic is mandatory for applications as in cosmetics, food, or medicine. In view of their interaction with vital tissues and their medical eligibility, a brief digression into biomimetic adhesives is given.