This book is for biology, physics, and engineering students who want to learn about the principles of protein mechanics and how it applies to the morphology and motility of cells. Part I explains how small particles like proteins respond to mechanical, thermal, and chemical forces, Part II focuses on cytoskeletal filaments, and Part III focuses on motor proteins. Chapters are centered on topics such as structure, chemistry, and mechanics, and different filaments or motors are discussed together. All concepts are introduced from first principles, and numerous boxed examples and figures aid the nonmathematical reader. For the mathematically inclined, detailed proofs of important results are included in the Appendix.