Ballast weight is something that is added to a race car to alter its performance.

In most racing series, cars have a minimum weight. Often, the actual weight of the car is lower, so ballast is used to bring it up to the minimum. The advantage is that the ballast can be positioned to affect the car's handling by changing its load distribution. This is near-universal in Formula 1.

In some racing series, for example the British Touring Car Championship

British Touring Car Championship

The British Touring Car Championship is a touring car racing series held each year in the United Kingdom. The Championship was established in 1958 as the British Saloon Car Championship and has run to various rules over the years – "production cars", then FIA Group 1 or 2 in the late 1960s...

, ballast is used as a handicap, the leading drivers at the end of one race being given more ballast for the next race.