This course presents an introduction to the physics of magnetospheres, including basic structures and dynamics, along with comparisons between magnetospheres in our solar wind system and those hypothesized in exoplanetary systems. The semester will be divided into three sections. 1) Foundations of Plasma Physics in Magnetospheres, covering particle drifts, adiabatic invariants, magnetohydrodynamics, dynamos, and particle acceleration. 2) Magnetospheres of Solar System Planets, comparing the intrinsic and induced magnetospheres in our solar system and the methods we have for measuring and modeling them. 3) Exoplanetary Magnetospheres and Star–Planet Interactions, focusing on what we know about general stellar-planetary interactions and the impact of stellar winds on planetary atmosphere and habitability.