The term “ nite Fermi systems” usually refers to systems where the fermionic nature of the constituents is of dominating importance but the nite spatial extent also cannot be ignored. Historically the prominent examples were atoms, molecules, and nuclei. These should be seen in contrast to solid-state systems, where an in nite extent is usually a good approximation. Recently, new and different types of nite Fermi systems have become important, most noticeably metallic clusters, quantum dots, fermion traps, and compact stars. The theoretical description of nite Fermi systems has a long tradition and dev- oped over decades from most simple models to highly elaborate methods of ma- body theory. In fact, nite Fermi systems are the most demanding ground for theory as one often does not have any symmetry to simplify classi cation and as a possibly large but always nite particle number requires to take into account all particles. In spite of the practical complexity, most methods rely on simple and basic schemes which can be well understood in simple test cases. We therefore felt it a timely undertaking to offer a comprehensive view of the underlying theoretical ideas and techniques used for the description of such s- tems across physical disciplines. The book demonstrates how theoretical can be successively re ned from the Fermi gas via external potential and mean- eld m- els to various techniques for dealing with residual interactions, while following the universality of such concepts like shells and magic numbers across the application elds.