HPX (High Performance ParalleX) is a general purpose C++ runtime system for parallel and distributed applications of any scale. It strives to provide a unified programming model which transparently utilizes the available resources to achieve unprecedented levels of scalability. This library strictly adheres to the C++11 Standard and leverages the Boost C++ Libraries which makes HPX easy to use, highly optimized, and very portable. HPX is developed for conventional architectures including Linux-based systems, Windows, Mac, and the BlueGene/Q, as well as accelerators such as the Xeon Phi.