High energy neutrino astronomy

After a long period of development, high energy neutrino astrophysics is approaching a level of sensitivity which reaches below the upper bounds on extraterrestrial neutrino fluxes derived from observed fluxes of cosmics rays and gamma rays. The day when first positive observations will start to populate the neutrino sky could therefore be close. Neutrino astronomy will open a new observational window and has the potential to discover effects not visible in any other windows. This talk reviews physics goals and methods and experimental approaches underground, underwater and under ice, as well as innovative methods like radio, acoustic or air shower detection of neutrinos at ultra high energies.