This textbook was developed to provide graduate students in physics and astronomy at the University of Maryland with a comprehensive background in plasma physics. It was designed for a two-semester course, normally taken in the second year of graduate study by students who have completed the usual sequence of graduate courses in classical and statistical mechanics, electro-magnetism, and mathematical methods. It is a basic introduction to the field and assumes no background in plasma physics. Although it was intended as a graduate text, it could be used for an advanced undergraduate course by proper selection of material.