A tank truck (United States usage) or road tanker (United Kingdom usage, both commonly shortened to tanker) is a motor vehicle designed to carry liquefied loads, dry bulk cargo or gases on roads. The largest such vehicles are similar to railroad tank cars which are also designed to carry liquefied loads. Many variants exist due to the wide variety of liquids that can be transported. Tank trucks tend to be large; they may be insulated or non-insulated; pressurized or non-pressurized; and designed for single or multiple loads (often by means of internal divisions in their tank). Some are semi-trailer trucks. They are difficult to drive due to their high center of gravity.

Tank trucks are described by their size or volume capacity. Large trucks typically have capacities ranging from 5,500 to 9,000 US gallons (21,000 to 34,000 L; 4,600 to 7,500 imp gal).

A tank truck is distinguished by its shape, usually a cylindrical tank upon the vehicle lying horizontally. Some less visible distinctions amongst tank trucks have to do with their intended use: compliance with human food regulations, refrigeration capability, acid resistance, pressurization capability, and others.