  The purpose of these notes is to give a brief review of superfluidity in
neutron stars. After a short presentation explaining why and how superfluidity
is expected in the crust and core of neutron stars, consequences on thermal
evolution and rotational dynamics are discussed. The second part summarizes a
formalism that has been recently developped to describe the hydrodynamics of
superfluids or superconductors in the framework of general relativity. As an
application, one can compute the oscillations of a two-component relativistic
neutron star.
