[en] This book is an introduction to the quantum mechanics of the angular momentum. After a description of the operators of spin and orbital angular momentum and their commutation relations the coupling of angular momenta is discussed. Then irreducible tensor operators are considered. Thereafter spherical harmonics are introduced together with correlation functions. In this connection the spherical harmonics is described. Thereafter the density matrix is considered with regards to polarization. Finally applications in scattering theory and many-body problems are considered. (HSI)