His Majesty's hired armed schooner Lady Charlotte served the British Royal Navy on contract between 28 October 1799 and 28 October 1801. She had a burthen of 120 85⁄94 tons (bm), and was armed with twelve 12-pounder carronades. As a hired armed vessel she captured several privateers and recaptured a number of British merchant vessels. After her service with the Royal Navy, she apparently sailed as a letter of marque until the French captured her in 1806.
She may have been re-rigged as a brig early in her career as most of the mentions of her refer to her as the "hired brig Lady Charlotte".
In 1799 to 1800 she was under the command of Lieutenant S. Halliday.
In January 1801, Lady Charlotte was under the command of Lieutenant George Morris. That month she captured the brig D'Eendraght.
On 11 February, Lady Charlotte was in Plymouth Sound when she sighted a vessel and gave chase. Eventually Lady Charlotte was able to capture the lugger Espoir. Espoir was armed with two brass 4-pounder and four iron 2-pounder guns, and had a crew of 23 men. She was two days out of Cherbourg and had not taken any prizes. Because of the strength of the wind, Lady Charlotte was not able to take prisoners off nor put a prize crew on board so she escorted her prize into port.
Around 18 March, HMS Scout was in company with the hired armed vessels Sheerness and Lady Charlotte when they captured a large Dutch East Indiaman off St Alban's Head. She was Crown Prince, of 1,400 tons and 18 guns, and had been sailing from China to Copenhagen with a cargo of tea. Because Sheerness and Lady Charlotte had sailed under Admiral Milbanke's orders, he and Admiral Hollowly were entitled to a share of the cargo, which was of "immense value".
On 29 March Lady Charlotte went in chase of the brig Friendship, which had been sailing from London to Dublin when a French privateer had taken her off Portland. Sheerness captured the privateer Pluton, the privateer in question, some six leagues north of La Hogue. The hired armed cutter Union recaptured Friendship on the night of the 29th.