The book "Optimal Control" offers a comprehensive introduction to the theory of optimal control, based on a one-year course at the Far Eastern Federal University in Vladivostok, Russia. It addresses both linear and nonlinear systems, placing particular emphasis on the necessary and sufficient conditions for optimal processes. The first half of the book focuses on the theory of linear control systems, discussing concepts such as the separation principle and reachability sets. The authors analyze various aspects such as controllability, observability, and terminal control. In the second half, nonlinear control is addressed, employing methods such as the variational method and the Lagrange multiplier rule. The book includes numerous exercises and additional tasks to help readers deepen their practical understanding of the theoretical knowledge.