In aviation terminology, a rejected takeoff (RTO) or aborted takeoff is the situation in which it is decided to abort the takeoff of an airplane.

There can be many reasons for deciding to perform a rejected takeoff, but they are usually due to a suspected or actual problem with the aircraft, such as an engine failure; fire; incorrect configuration; aircraft controllability; environmental conditions such as predictive windshear; or an instruction from Air Traffic Control.

There are three phases of a takeoff. In the low-speed regime, usually below 80 kts or so, the takeoff will be rejected even for minor failures. In the high-speed regime, above usually 80 kts but below V₁, minor problems are ignored, but the takeoff will still be rejected for serious problems, in particular for engine failures. The takeoff decision speed, known as V₁, is calculated before each flight for larger multi-engine airplanes. Below the decision speed, the airplane should be able to stop safely before the end of the runway. Above the decision speed, the airplane may overshoot the runway if the takeoff is aborted, and, therefore, a rejected takeoff is normally not performed above this speed, unless there is reason to doubt the airplane's ability to fly. If a serious failure occurs or is suspected above V₁, but the airplane's ability to fly is not in doubt, the takeoff is continued despite the (suspected) failure, and the airplane will attempt to land again as soon as possible. If the airplane's ability to fly is in doubt (for instance, in the event of a major flight-control failure which leaves the airplane unable to rotate for liftoff), the best option may well be to reject the takeoff even if after V₁, accepting the likelihood of a runway overrun.

Single-engine aircraft will reject any takeoff after an engine failure, regardless of speed, as there is no power available to continue the takeoff. Even if the airplane is already airborne, if sufficient runway remains, an attempt to land straight ahead on the runway may be made. This may also apply to some light twin-engine airplanes.

Before the takeoff roll is started, the autobrake system of the aircraft, if available, is armed. The autobrake system will automatically apply maximum brakes if throttle is reduced to idle or reverse thrust during the takeoff roll once a preset speed has been reached.