The act 39 & 40 Geo. 3. c. 87, sometimes called the Thames Police Act 1800, the Thames River Police Act 1800, the Marine Police Act or the Depredations on the Thames Act 1800, was an act of the Parliament of Great Britain, granted royal assent on 28 July 1800. As alluded to in its long title, it amended the Thefts upon the Thames Act 1762.