The Local Group is especially suited as a laboratory for studying the effects of the massive star population on the galactic environment. There are three types of massive star feedback: 1. Radiative feedback, i.e., ionizing emission, which results in photoionized nebulae and diffuse, warm (104 K) ionized gas; 2. Mechanical feedback, predominantly from supernovae (SNe), resulting in supernova remnants (SNRs), superbubbles, and galactic superwinds; and 3. Chemical feedback from nucleosynthesis in SNe and massive star evolution, which drives galactic chemical evolution. Since the last will be reviewed by Don Garnett and Monica Tosi in this volume, I will address here only the radiative and mechanical feedback processes.
Only in the Local Group can we spatially resolve the the various physical parameters that determine, and result from, the interaction of massive stars with their immediate environment. Radiative and mechanical feedback return large quantities of energy to the galactic environment, both with luminosities log L of order 36 - 41 erg s-1 for typical OB associations. These processes may dominate the balance between different temperature phases of the interstellar medium (ISM), profoundly affecting the structure and kinematics of the ISM, star formation, and other evolutionary processes in star-forming galaxies.