The task of this paper was to describe ship electrical systems, so the ship was considered as a separate electrical power system. The systems for the production, transmission and consumption of electrical energy are described. The medium-voltage ship electrical power system, safety and protection measures are also briefly described, and the history of ship electrification is also touched upon. The introductory chapter briefly discusses the development of ship electrification and briefly touches on sources, consumers and transmission of electrical energy on board. The second chapter discusses in more detail the main and auxiliary sources of electrical energy, i.e. generators, batteries, shore connection and uninterruptible power supply. The third chapter generally discusses ship electrical networks, electrical energy distribution systems and transmission systems for electric propulsion. The fourth chapter describes electrical energy consumers, which are divided into four subchapters. The first subchapter describes electric motor drives, the second describes circuit consumers, the third describes lighting consumers, while the fourth subchapter lists other consumers. Chapter 5 discusses the medium-voltage shipboard electrical power system and the protection of shipboard electrical equipment and persons on board. It also discusses the protection of ships from lightning strikes.