An inner tube is an inflatable torus that forms the interior of some pneumatic tires.^[1] The tube is inflated with a valve stem, and fits inside of the casing of the tire. The inflated inner tube provides structural support and suspension, while the outer tire provides grip and protects the more fragile tube.

Nowadays most bicycle tires use inner tubes, inner tubes are also used in things such as dolly carts, wheelbarrows, and are also used in many motorcycles. Tires on things such as cars used to have inner tubes but most cars have switched to tubeless tires which rely on air and no inner tube. They are now less common in cars ^{[clarification needed]} because of the benefits of having no tube, such as the ability to operate at low pressure and at high pressure (unlike a tube tire, which would pinch at low pressure and burst at high pressure), without going flat.^[2] Large inner tubes are used for different types of recreation such as using them for flotation devices in activities known as tubing.

Inner tubes were invented in the 1800s to be used for pneumatic tires, the standard wheels of the time where not air filled thus making them uncomfortable to ride on. Over the years they started to make inner tubes of colors other than black such as red, white, and grey, these inner tubes were known to be made of more natural rubber than the standard black tube which made them more flexible. Inner tubes were used in tires for a wide range of uses including cars and trucks but in the 1950s-1970s tubeless tires started to become dominant for cars and trucks.

The tube is usually made out of a mix of natural and synthetic rubber.^[3] Natural rubber is less prone to punctures and is often more pliable, while synthetic rubber is cheaper. Often racing bikes will have a higher percentage of natural rubber than regular bikes. Some manufacturers have branched out to making other types of bike inner tubes such as latex and TPU inner tubes.

Inner tubes tend to be slower than tubeless tires because of the friction between the casing and the inner tube. Tires that use tubes are on average lighter, as the tube can be made relatively thin, however latex and TPU inner tubes are made to be lighter and more comfortable to ride on.

Bead tires, either with an inner tube or tubeless, can not be ridden flat, as the tire may separate from the rim. On the other hand, on tubular tires the tubing is sown to the tire, and if punctured, the tire can still be ridden flat.^[3] Tubeless tires are reportedly more comfortable to use, if attached to the bicycle properly.^[1][2][3]

• Tubeless tires