A fuel tax (also known as a petrol tax, gasoline tax, gas tax or fuel duty) is a sales tax imposed on the sale of fuel. In most countries, the fuel tax imposed on fuels which are intended for transportation. Fuels used to power agricultural vehicles, and/or home heating oil which is similar to diesel are taxed at a different, usually lower, rate.

In the United States, the fuel tax receipts are often dedicated or hypothecated to transportation projects so that the fuel tax is considered by many a user fee. In other countries, the fuel tax is a source of general revenue.