'Silicon Photonics: Electromagnetic theory' is a concise introduction to the fundamental theories of integrated optics that focuses on modern silicon photonic technology. It includes well-known general theories on properties of waveguides and couplers as well as new theories on high-index contrast waveguides, directional couplers, and micro-ring resonators. The book may be used as a first introduction to integrated optics, with only basic electrodynamics as prerequisite. It would fit well as lecture material in a short introduction course, as additional material in an extensive electrodynamics course, or as fundamental background material in a more applied course. The later chapters are of interest to experts in the field of integrated optics that want to learn the latest theories for high-index contrast waveguides such as silicon photonic waveguides.