This text is designed as a practical introduction to quantum chemistry. Quantum chemistry is applied to explain and predict molecular spectroscopy and the electronic structure of atoms and molecules. In addition, the text provides a practical guide to using molecular mechanics and electronic structure computations including ab initio, semi-empirical, and density functional methods. The use of electronic structure computations is a timely subject as its applications in both theoretical and experimental chemical research is increasingly prevalent. This text is written in a format that fosters mastery of the subject both in competency in the mathematics and in obtaining a conceptual understanding of quantum mechanics..