Which of these historical figures was the oldest at the time of their execution?

The eldest of the historical figures listed at the time of their execution was Mary, Queen of Scots (8 December 1542 – 8 February 1587), also known as Mary Stuart or Mary I of Scotland, who reigned over Scotland from 14 December 1542 until her forced abdication on 24 July 1567.

Mary had once claimed Elizabeth I's throne as her own and was considered the legitimate sovereign of England by many English Catholics, including participants in a rebellion known as the Rising of the North. Perceiving Mary as a threat, Elizabeth had her confined in various castles and manor houses in the interior of England. After over eighteen years in custody, Mary was found guilty of plotting to assassinate Elizabeth in 1586, and was beheaded the following year at Fotheringhay Castle.

Joan of Arc (c. 1412 – 30 May 1431), nicknamed "The Maid of Orléans", is considered a heroine of France for her role during the Lancastrian phase of the Hundred Years' War, and was canonized as a saint. She was handed over to the English and put on trial by the pro-English bishop, Pierre Cauchon, on a variety of charges. After Cauchon declared her guilty, she was burned at the stake on 30 May 1431, dying at about nineteen years of age.

Anne Boleyn (c. 1501 – 19 May 1536) was Queen of England from 1533 to 1536, as the second wife of King Henry VIII. She was beheaded for treason aged 35.

Marie Antoinette (2 November 1755 – 16 October 1793) was the last queen of France before the French Revolution.