Molecular spectroscopy provides a straightforward introduction to the spectroscopy of diatomic molecules and is written at the level of intermediate undergraduate courses in physical chemistry and chemical physics. Following a general introduction to the subject, Chapter 2 lays out the essential quantum mechanical tools required to understand spectroscopy. Chapter 3 uses this quantum mechanical framework to establish the selection rules which govern spectroscopic transitions. Chapters 4-8 describe the various branches of spectroscopy covered by the book: rotational, rotational-vibrational, Raman, electronic, and photoelectron spectroscopy. Very little previous knowledge is assumed and mathematics is kept to a minimum. The author uses a range of examples to describe how spectra arise and what information on the structure of the molecules can be acquired from their study.