The Software Foundations series is a broad introduction to the mathematical underpinnings of reliable software. The principal novelty of the series is that every detail is one hundred percent formalized and machine-checked: the entire text of each volume, including the exercises, is literally a "proof script" for the Coq proof assistant. The exposition is intended for a broad range of readers, from advanced undergraduates to PhD students and researchers. No specific background in logic or programming languages is assumed, though a degree of mathematical maturity is helpful. A one-semester course can expect to cover Logical Foundations plus most of Programming Language Foundations or Verified Functional Algorithms, or selections from both.