Quantum field theory has been with us for over 75 years, but it is only in the last 25 that physicists and mathematicians have jointly ventured out to explore its realms beyond the reach of perturbation theory, to the great benefit of both disciplines. Conformal Field Theory consists of pedagogical lectures delivered at the Feza Gursey Institute, Istanbul, in the summer of 1998 on some of these non-perturbative approaches. The topics of these lectures are central to our emerging understanding of conformal field theory and its importance to both statistical mechanics and string theory....