Mary Eleanor Bowes, Countess of Strathmore and Kinghorne (24 February 1749 – 28 April 1800), known as "The Unhappy Countess", was an 18th century British heiress, notorious for her licentious lifestyle, who was married at one time to the 9th Earl of Strathmore and Kinghorne. She and the Earl are ancestors of Queen Elizabeth II.
Mary was born the daughter and heiress of George Bowes, a wealthy businessman. Bowes died when Mary was 11 years old, and left her a vast fortune (estimated at between £600,000 and £1,040,000), which he had built up through control of a cartel of coal-mine owners. At a stroke, Mary became the wealthiest heiress in Britain, perhaps in all of Europe. She encouraged the attentions of Campbell Scott, younger brother of the Duke of Buccleuch as well as of John Stuart, the self-styled Lord Mountstuart, eldest son of Lord Bute (the Prime Minister), before becoming engaged at the age of 16 to John Lyon, the 9th Earl of Strathmore and Kinghorne.
Mary married the 9th Earl of Strathmore on her 18th birthday, 24 February 1767.