Autonomous performance of ships is essential for minimizing human errors in navigation and for efficient operation of ships under harsh environmental conditions. This task is challenging due to the nonlinearities of ship dynamics, modeling imprecision, under-actuated ship configuration along with unpredictable environmental disturbances. This book addresses the guidance and control problem of ships for the purpose of full automation of under-actuated ships. A nonlinear dynamic model of the ship is provided as a test-bed for the developed controllers. A set of robust controllers and observers in addition to a new guidance system are provided as well. Finally, the work includes the integration of the guidance system with the controllers and observers for the purpose of obtaining a fully autonomous under-actuated ship. The targeted readers of this book are the modeling and controls community. In particular, marine engineering students that are dealing with the control of ships. Furthermore, the book should be of interest for undergraduate and graduate engineering students that are taking advanced control classes that deal with modeling and control of nonlinear dynamic problems.