Title: Horosphere boundary and extension of biholomorphisms Abstract. This is a joint work with Filippo Bracci. Given a complete hyperbolic manifold (in the sense of Kobayashi), we consider an abstract boundary inspired by the one dimensional Caratheodory's prime ends theory. That boundary may be homeomorphic to the Euclidean boundary and to the Gromov boundary (this is the case for strongly pseudoconvex domains in the complex Euclidean space) or may be topologically different from these two boundaries (this is the case for the bidisc). We use the construction of that boundary and results from the Gromov hyperbolicity theory to study continuous extension of biholomorphisms between certain non smooth domains.