Novelist and philanthropist. Born in Edinburgh, the daughter of reformer Sir John Sinclair of Ulbster. She acted as her father's secretary, but after his death began to write children's books, including her noted Holiday House (1839), romantic novels and travel guides, publishing some 28 works. Her travel books included works on Scotland, Wales and Shetland. It was Sinclair who first guessed that Sir Walter Scott (1771 - 1832) was the author of the anonymous Waverley Novels. She also was noted for her philanthropic works; namely introducing worker's canteens in Edinburgh and funding the first street fountain at the west end of Princes Street. Her Volunteer Brigade for the boys of Leith was the first of its kind.
Sinclair is remembered by a grand Gothic memorial located at the western end of Edinburgh's Queen Street.