Geometric Function Theory is a central part of Complex Analysis (one complex variable). "The Handbook of Complex Analysis - Geometric Function Theory" deals with this field and its many ramifications and relations to other areas of mathematics and physics. The theory of conformal and quasiconformal mappings plays a central role in this Handbook, for example a priori-estimates for these mappings which arise from solving extremal problems, and constructive methods are considered. As a new field, the theory of circle packings which goes back to P. Koebe is included. The Handbook should be useful for experts as well as for mathematicians working in other areas, as well as for physicists and engineers. It includes a collection of independent survey articles in the field of Geometric Function Theory. It includes existence of theorems and qualitative properties of conformal and quasiconformal mappings. It also contains a bibliography, including many hints to applications in electrostatics, heat conduction, and potential flows (in the plane).