Classical and Quantum Parametric Phenomena provides an overview of the phenomena arising when parametric pumping is applied to oscillators. These phenomena include parametric amplification, noise squeezing, spontaneous symmetry breaking, activated switching, cat states, and synthetic Ising spin lattices. To understand these effects, topics such as nonlinear and stochastic dynamics, coupled systems, and quantum mechanics are introduced. Throughout the book, introductions are kept as succinct as possible and attention is focused on understanding parametric oscillators. As a result, the text helps readers to familiarize themselves with many aspects of parametric systems and understand the common theoretical origin of nanomechanical sensors, optical amplifiers, and superconducting qubits. Parametric phenomena have enabled important scientific breakthroughs over the last decades and are still at the focus of intense research efforts. This book provides a resource for experimental and theoretical physicists entering the field or wishing to gain a deeper understanding of the underlying connections. This includes combining formal and intuitive explanations, accompanied by exercises based on numerical Python codes. This combination allows readers to experience parametric phenomena from various directions and apply their understanding directly to their own projects.