Stellar evolution as a research area investigates the physical processes governing the formation, structural changes, and end states of stars across cosmic time, using stellar structure theory, nuclear astrophysics, hydrodynamics, and radiative transfer. It encompasses modeling of protostellar collapse, main-sequence hydrogen burning, post–main-sequence shell burning, and advanced nucleosynthesis up to core collapse or thermonuclear disruption, as well as mass loss, rotation, magnetic fields, and binary interactions. The field integrates observations (e.g., HR diagrams, asteroseismology, stellar populations) with numerical simulations to constrain stellar lifetimes, remnant formation (white dwarfs, neutron stars, black holes), and the chemical and energetic feedback of stars into galaxies.