This volume contains detailed expositions of talks given during an instructional conference held at Luminy in December 1998, which was devoted to classical and recent results concerning the fundamental group of algebraic curves, especially over finite and local fields. The scientific guidance of the conference was supplied by M. Raynaud, a leading expert in the field. The purpose of this volume is twofold. Firstly, it gives an account of basic results concerning rigid geometry, stable curves, and algebraic fundamental groups, in a form which should make them largely accessible to graduate students mastering a basic course in modern algebraic geometry. However classic, most of this material has not appeared in book form yet. In particular, the semi-stable reduction theorem for curves is covered with special care, including various detailed proofs. Secondly, it presents self-contained expositions of important recent developments, including the work of Tamagawa on Grothendieck's anabelian conjecture for curves over finite fields, and the solution by Raynaud and Harbater of Abhyankar's conjecture about coverings of affine curves in positive characteristic. These expositions should be accessible to research students who have read the previous chapters. They are also aimed at experts in number theory and algebraic geometry who want to read a streamlined account of these recent advances.