SHARK is a versatile and high-performance open-source library for machine learning, developed in C++. It encompasses a variety of techniques, including both linear and nonlinear optimization, kernel methods, neural networks, and more. This library serves as an essential resource for both practical applications and academic research endeavors. Built on top of Boost and CMake, SHARK is designed to be cross-platform, supporting operating systems such as Windows, Solaris, MacOS X, and Linux. It operates under the flexible GNU Lesser General Public License, allowing for broad usage and distribution. With a strong balance between flexibility, user-friendliness, and computational performance, SHARK includes a wide array of algorithms from diverse fields of machine learning and computational intelligence, facilitating easy integration and extension. Moreover, it boasts unique algorithms that, to the best of our knowledge, are not available in any other competing frameworks. This makes SHARK a particularly valuable tool for developers and researchers alike.