Trolleybuses (also known as trolleybuses, trolleybuses, trolleybuses, trolleybuses or trolleybuses) are electric buses that use spring-loaded pole poles to draw power from overhead lines (usually suspended on roadside posts). Two wires and two poles are needed to complete the circuit. This is different from the tram or tram, which usually uses the track as the return path and only needs a wire and a pole (or pantograph). They are also different from other types of electric buses that usually rely on batteries. Power is usually supplied at 600 VDC, with some exceptions.

At present, there are about 300 kinds of trolleybus systems in operation in 43 countries. There are more than 800 trolleybus systems in total, but no more than 400 concurrent systems.

Trolleybuses are not common in North America today, but they are still common in many European countries as well as Russia and China. They usually occupy a certain position in the use of street Railways (trolleybuses) and diesel buses. Today, trolleybuses provide services in about 300 cities or metropolitan areas around the world.

At present, there are 300 cities or large cities operating trolleybuses, and there have been more than 500 additional trolleybus systems in the past. For an overview of trolleybuses by country, see trolleybuses by country, and a complete list of trolleybus systems by location, as well as opening and (if applicable) closing dates, see the list of trolleybus systems and the related list indexed here.

As of 2012, most of the existing systems are located in Europe and Asia, including 85 in Russia and 43 in Ukraine. However, there are eight systems in North America and nine in South America.

Trolleybuses are preserved in most of the countries in which they operate. Britain has the largest number of trolleybuses, more than 110, while the United States has the largest number of trolleybuses. Most of the preserved vehicles are only on static display, while some museums are equipped with trolleybus lines, allowing trolleybuses to serve tourists. There are three museums with operable trolley routes in the UK – the trolley Museum in santovte, the Transport Museum in East Anglia and the black country life Museum – and three in the US – the Illinois Railway Museum, the coastal trolley Museum and the shoreline trolley Museum – but in these museums, the operation of trolley buses varies It will be carried out regularly.