The Electrostar is a collective name given to the hugely successful class of EMUs produced by Bombardier at its Derby factory. There have been seven different classes that come under the Electrostar umbrella, all working mainly in the south-east of the country. The first unit was delivered in 1999 to replace the Class 302 units on the London, Tilbury & Southend route. Over the following eighteen years, a total of 480 sets were produced for a variety of operators.

The different classes are all configured to their specific routes, with most making up a standard four-car train, although some of the later Class 377 units were delivered as five-car train. The Class 376 units are high-density units, and were the only members of the Electrostar family delivered without gangway doors on the front.

The fleets were introduced to eradicate the earlier slam-door stock that was in use widely in the south-east at the time. Some classes are also fitted out for AC operation, and can be seen working as far north as Peterborough on the East Coast Main Line, and also Milton Keynes on the West Coast Main Line.

The design was also used on an export order, with twenty-four sets being used by Gautrain in South Africa.

Today the whole fleet is still in use, and this book aims to show the different classes in their everyday use.