Optical waveguides is a concept encompassing structures designed to confine and guide electromagnetic waves, typically light, along a defined path through controlled total internal reflection or other waveguiding mechanisms. As an academic field, it investigates the principles of light propagation within these structures, explores the design, fabrication, and characterization of various waveguide geometries and materials, and develops their application in integrated photonics, optical communication, sensing, and nonlinear optics.