A calculus-based introduction to the observations and theoretical understanding of the structure and evolution of stars. Topics include astrometry, photometry, spectroscopy, the Planck function of thermal emission, cause of spectral emission and absorption lines, Boltzmann and Saha distributions of atomic energy levels and ionization states, the Hertzprung Russell diagram, binary stars and stellar mass determination, nuclear energy generation in stars, hydrodynamic equilibrium, equations of state, and the fates of stars.