Optical and quantum electronics represent dynamic interdisciplinary fields that merge photonics, quantum mechanics, and semiconductor physics to develop game-changing technologies. This chapter overviews the fundamental theories, devices, and applications that define current optical and quantum electronic systems. The chapter first outlines the history and basic optical phenomena associated with light propagation, diffraction, and light–matter interaction before discussing photonic devices, such as lasers and light-emitting diodes (LEDs) and optical fibers, that ultimately drive the communications systems in a global network. The chapter then discusses quantum mechanics and its significant contribution to understanding electronic systems, including quantum tunneling, quantization, and entanglement. The main topics in quantum optics, such as single-photon sources, quantum interference, and measurement, are discussed in parallel with the new quantum devices, such as quantum dot lasers and superconducting qubits. Finally, the chapter outlines challenges, including decoherence and scalability in quantum electronics, while providing future outlooks encompassing advanced photonic materials, quantum networks, and sustainable design strategies.