Proceedings, 2011 European School of High-Energy Physics (ESHEP 2011): Cheile Gradistei, Romania, September 7-20, 2011

The European School of High-Energy Physics is intended to give young physicists an introduction to the theoretical aspects of recent advances in elementary particle physics. These proceedings contain lecture notes on quantum field theory and the Standard Model, quantum chromodynamics, flavour physics, neutrino physics, physics beyond the Standard Model, cosmology, heavy ion physics, statistical data analysis, as well as an account for the physics results with the data accumulated during the first run of the LHC.