World's Fastest Car: 431 km/h (268 mph)

Currently the world's fastest street-legal production car (as opposed to concept cars or modified cars) is the Bugatti Veyron Super Sport which can reach a speed of 431 km/h (268 mph). 

While only 5 of the World Record model were made out of a total of 30 Super Sports, the other 25 Super Sports will all also achieve this speed with the limiter turned off. After a review by a panel of experts, Guinness considers this not to be a modification, and thus it is eligible for the record