Mary Lacy (1740-1801) was a lady who served in the Royal navy and left memoirs of her experiences.
Lacy ran away from home dressed as a boy at the age of nineteen in 1759, and worked as a servant for a ship's carpenter of the British navy under the name William Chandler until 1763. She then studied as an apprentice to be a shipwright. In 1770, she took her exam as a shipwright, arguably the first of her gender to have done so. In 1771, however, she was forced to stop working because of her rheumatism, and applied for a pension from the admiralty under her legal name, Mary Lacy, which was granted.
In 1772 she married Josias Slade, a shipwright, of Deptford, Kent and in 1773 published her memoirs The Female Shipwright. The couple had six children.