This book provides a modern introduction to the study of star formation, at a level suitable for graduate students or advanced undergraduates in astrophysics. The first third of the book provides a review of the observational phenomenology and then the basic physical processes that are important for star formation. The remainder then discusses the major observational results and theoretical models for star formation on scales from galactic down to planetary. The book includes recommendations for complementary reading from the research literature, as well as five problem sets with solutions.