Margaret Beaton, Lady Reres (floruit 1560–1580) was a Scottish courtier and companion of Mary of Guise and Mary, Queen of Scots. She was blamed by the enemies of Mary, Queen of Scots, for her involvement in alleged immorality at court.

Margaret Beaton was a daughter of John Beaton of Creich, Keeper of Falkland Palace and Jane Hay, a daughter of the Provost of Dundee. Mary Beaton, one of Mary, Queen of Scots four companions was her niece, the daughter of her brother Robert Beaton of Creich.

She married Arthur Forbes of Reres or Rires Castle in Kilconquhar, Fife, and was then called "Lady Reres". The place-name was sometimes written "Reresse". On 22 December 1558 Mary of Guise paid her £300.

In September 1566 she was part of the household of James VI of Scotland at Stirling Castle, provided with a bed with curtains made from blue wool cloth called "ostage". Mary sent her two coffers for the prince's chamber. In December 1566 Mary bought her a gown of black velvet with black satin sleeves and skirt front, probably to wear at the baptism of Prince James.

In April 1570 Forbes was involved in the murder of Mr John Wood, secretary of Mary's half-brother Regent Moray. Their son John Forbes was killed in the struggle. Margaret Beaton held a grudge against John Wood's wider family, who lived at Largo. This animosity had led to the allegations against her. Margaret featured in stories about Mary, Queen of Scots, written as propaganda by the queen's enemies, which overshadow the few facts known about her role at court.

Lord Darnley's chamber servant Thomas Nelson said that Mary, Queen of Scots and Lady Reres used to play and sing in the garden at Kirk o'Field at night time. This was his explanation why Mary's servants Archibald Beaton and Nicolas Hubert alias French Paris had keys. Margaret Beaton, her sister Janet Beaton, and Jean Hepburn were said to Mary's attendants at Dunbar Castle, after Bothwell had abducted her, before the battle of Carberry Hill.

George Buchanan wrote that she was old and fat in the 1560s, "a woman very heavy both by unweildy age and massy substance", and had been a mistress of James Hepburn, 4th Earl of Bothwell. He tells a story of Mary and Margaret Carwood helping Lady Reres with her girdle or belt to climb down a garden wall in Edinburgh's Cowgate in order to bring the Earl of Bothwell to a secret liaison with the queen.

This incident or story was also described with more detail at the York Conference in 1568 and recorded in a document called the "Book of Articles";