The Large Hadron Collider (LHC) at CERN is the largest and most complex single experiment ever performed in the history of mankind. The physics program of the LHC is motivated by fundamental questions about the laws of nature, such as explaining the origin of mass, understanding the early universe and the structure of space and time, unravelling the nature of dark matter and providing glimpses of extra spatial dimensions or grand unification of forces. Any of these insights would definitely constitute a revolution in our view on the world. The LHCPhenoNet unites throughout Europe young and energetic leadership in theoretical particle physics with emphasis on LHC phenomenology. Most of its team and task leaders have made highly significant and innovative contributions in the last years within the theory of strong interactions, Quantum Chromodynamics (QCD), or the electroweak sector of the SM by addressing key issues at the interface to the experiments. The network members are poised to lead the theoretical particle physics community to meet the new challenges presented by LHC physics and to provide in a unified European effort excellent training for young theoretical physicists in this field, at both the doctoral and post-doctoral level. With the challenges of the machine operation driving the LHC start-up, the proposed timeline of the initial training network matches the currently foreseen LHC running schedule and thus allows full exploitation and interpretation of the early data. The field of theoretical particle physics is also currently driven by the development of customized open-source software as well as by applications of products from commercial enterprises especially in the field of symbolic manipulation and computer algebra, such as Maple and Mathematica from our private sector partners. The proposed network LHCPhenoNet is designed to provide optimal training conditions for early stage researchers in an interdisciplinary environment.