The first edition of the textbook on the Geology of Tamil Nadu and Pondicherry, authored by Shri K.S. Subramanian and Dr. T.A. Selvan, was brought out in the year 2001. Since then, a wealth of new geoscientific data has been generated through extensive research by several workers especially in the Southern Granulite Terrain (SGT) of Tamil Nadu. These new geochronological and geochemical data generated in the central and southern parts of Tamil Nadu have immensely helped in better understanding of the overall tectonic evolution of the SGT. In order to present these new data and the interpretations thereof, the Society has taken up revision of the text book on Geology of Tamil Nadu and Puducherry through this second edition. A major departure has been made by the authors in this revised edition in treating the geology of Tamil Nadu by describing the lithoassemblages tectonic block-wise (instead of age-wise), in view of the importance of the plate-tectonic concept being adopted in the evolution of the Dharwar Craton and the SGT. This edition has been richly benefited from the extensive geoscientific data generated by the Geological Survey of India as well as other institutions involved in geoscientific research in Tamil Nadu and Puducherry. The authors have made all efforts to synthesize and incorporate all the new data published till recently to give as far as possible an up-to-date geological information for the benefit of the readers. It is sincerely hoped that the readers, especially the student community and young researchers, will get the benefit of going through the existing database and identify critical problems / areas where further research can be taken up for better understanding of the overall tectonic evolution of the granulite terrain of Tamil Nadu and for locating new mineral deposits.