What is the name of the flag that indicates a race is suspended?

The flag that indicates a race is suspended is the red flag.

In motorsport, officials display a solid red flag when conditions are too dangerous for drivers to continue. The interruption may be caused by heavy rain, lightning, a blocked circuit, debris, damaged barriers, a fire, or a serious crash. Drivers must slow down and follow the series’ instructions, usually returning to the pit lane or stopping at a designated point.

A red flag does not necessarily mean the event is over. In Formula 1, race control may pause the session while marshals clear the track, repair barriers, or attend to an incident. The race can later restart, sometimes from a standing start or behind the safety car, depending on the circumstances and regulations.

A common mix-up is the yellow flag: it warns drivers about a local hazard and normally prohibits overtaking, but the session continues. The chequered flag, by contrast, signals the end of a session or race.