The train is a vehicle sporadically used for transportation in the world. They are known to carry both passengers and cargo. Although not exclusive to any one nation, trains tend to be found in industrialized areas, namely cities. They usually run on rails, but they are also known to run without them.
A tank train was used by Azula, Mai, and Ty Lee when chasing Team Avatar through the Earth Kingdom. The train left track-marks wherever it drove, which was how Zuko was eventually able to find them. Being a tank train, it did not run on rails and traveled at very high speeds. Smoke billowed through a pipe on the top of the train, implying that it likely ran on coal.
In another occasion, Aang, Sokka, Sho, and Combustion Man boarded a train in the Fire Nation. Unlike tank trains, it ran on tracks and had stations that were built specifically for the train's use. However, it also appeared to be powered by coal. Later on in the journey, Combustion Man attacked Aang and Sokka, who were unaware of his presence. The train was wrecked in the battle and subsequently decommissioned.
By the time of Avatar Korra's arrival at Republic City in 170 AG, trains had become more advanced and common, despite facing competition from a new form of transportation known as the automobile. A large terminal, known as Central City Station, was constructed in downtown Republic City; it quickly became a bustling center of commerce. It is the only known station that transports both passengers and cargo. To commemorate the former Fire Lord, Zuko, a statue depicting him firebending was built outside the station.
- Elevated railway train - A type of train that runs on the elevated tracks of Republic City. It is a common form of public transportation and cargo shipping. The train cars are painted red.
- Fire Nation train - A train used for public transportation in the Fire Nation. It ran on tracks and stopped at multiple stations, where passengers could board the train or exit it. The train was composed of a metal engine and several wooden passenger cars that followed behind it. The engine was decorated with three Fire Nation insignias, one small insignia on the front and two larger insignias on the sides. On the top of the car, there was a chimney that let out smoke emitted by the engine. The passenger cars had glass windows that let in sunlight.
- Tank train - A hybrid vehicle that was designed to resemble both a tank and a train. It was manufactured in the Fire Nation and was used by Azula, Mai, and Ty Lee to chase Team Avatar. Although it did not run on rails like most trains do, it could travel at high speeds and traverse many types of terrain. It was powered by coal, which emitted smoke that would billow through a large pipe on the upper front of the train. The front of the train was equipped with an armored plow for better navigation and defense. The train also had two grappling hooks.
- In the days before the invasion of the Fire Nation, Aang had a dream where Katara's hair got caught in a train.