In this thesis, we study energy absorption in classical chaotic, ergodic systems subject to rapid periodic driving, and in related systems. Under a rapid periodic drive, we find that the energy evolution of chaotic systems appears as a random walk in energy space, which can be described as a process of energy diffusion. We characterize this process, and show that it generally predicts three stages of energy evolution: Initial relaxation to a prethermal state, followed by slow evolution of the system’s energy probability distribution in accordance with a Fokker-Planck equation, followed by either unbounded energy absorption or relaxation to an infinite temperature state. We then study the energy diffusion model in detail in driven billiard systems specifically; in particular, we obtain numerical results which corroborate the energy diffusion description for a specific choice of billiard. This is followed by an analysis of energy diffusion in one-dimensional oscillator systems subject to weak, correlated noise. Finally, we begin to investigate energy absorption in periodically driven quantum chaotic systems, i.e., quantum systems with a classical chaotic analogue. We invoke tools from Floquet theory and random matrix theory to investigate whether the classical energy diffusion framework can be applied to quantum systems, and under what conditions. We conclude with a discussion of potential models for energy absorption in quantum chaotic systems, and with an overview of open questions and directions for future work.