Q-car is an English Metropolitan Police term for an unmarked police vehicle used for covert patrolling and operations. It is often crewed by plain-clothed officers. A Q-car is usually a high-powered saloon or estate vehicle, fitted with sirens and blue warning lights behind the front grille in order for it to also carry out response duties when necessary.

The word "Q-car" is derived from Q-ship or Q-boat, which was a term given to Royal Navy armed vessels that were designed to look like unarmed merchants in order to counter the U-boat threat.