General relativity and the weak field approximation: the wave equation for the gravitational radiation. Astrophysical sources of gravitational waves. Computation of the gravitational signal emitted by coalescent binary systems. Gravitational collapse and its messengers. Gravitational radiation emitted by neutron stars. Stochastic background. The gravitational spectrum and the possible detection techniques: polarization of the cosmic microwave background, pulsar timing array. Experimental techniques in interferometric detectors. Introduction to data analysis techniques. Exploiting the synergies with electromagnetic and neutrino observations: the multi messenger approach. Recent results and their implications in fundamental physics, astrophysics and cosmology.