The concept of frustration in condensed matter physics was introduced in the context of spin glass in the 1970''s. Since then frustration was proven in certain crystalline magnetic materials and the field has matured to reveal a wealth of phenomena with implications far beyond magnetism: Frustrated systems host a range of non-trivial phases and phase transitions. The advantage to study frustration in magnetic systems is the possibility to experimentally investigate them and the diversity of theoretical tools available to describe their behaviour. In this context the comprehensive study of the paradigmatic model of classical triangular antiferromagnets was missing: this work proposes such a study. Phase diagrams of Heisenberg triangular antiferromagnet and anisotropic Heisenberg triangular antiferromagnets are calculated with a blend of theoretical analysis and numerical computations. This book should interest both graduate students and researchers who want to get familiar with frustration, with topological analysis of phase transitions and with classical Monte Carlo simulations. It should also interest researchers working on frustrated systems as a reference on a paradigmatic model.