Sarah Churchill (née Jenyns, spelt Jennings in most modern references), Duchess of Marlborough (June 5, 1660 (old style) – October 18, 1744) rises to be one of the most influential women in British history as a result of her close friendship with Queen Anne of Great Britain.

Sarah's friendship and influence with Princess Anne is widely known, and leading public figures often turn their attentions to her in the hope that she will influence Anne to comply with requests.

As a result, by the time Anne becomes queen, Sarah’s knowledge of government, and intimacy with the Queen, allows her to become a powerful friend and a dangerous enemy, the last in the long line of Stuart favorites.

In an age when marriage is principally for money, not love, Sarah enjoys an unusually close relationship with her husband, John Churchill, 1st Duke of Marlborough, whom she marries in 1677.

Sarah acts as Anne's agent after the latter's father, James II, is deposed during the Glorious Revolution; and she promotes her interests during the rule of James's successors, William III and Mary II.

When Anne comes to the throne after William's death in 1702, the Duke of Marlborough, together with Sidney Godolphin, the first Earl of Godolphin, rises to head the government, partly as a result of his wife's friendship with the queen.

While the Duke is out of the country commanding troops in the War of the Spanish Succession, Sarah keeps him informed of court intrigue, while he sends her requests and political advice that she then conveys to the Queen.

Sarah tirelessly campaigns on behalf of the Whigs, while also devoting much of her time to building projects such as Blenheim Palace.

She dies in 1744 at the age of eighty-four.

A strong-willed woman who likes to get her own way, Sarah tries the Queen's patience whenever she disagrees with her on political, court or church appointments.

After her final break with Anne in 1711, she is dismissed from the court with her husband, but she returns to favor under the Hanoverians after Anne's death.

She has famous subsequent disagreements with many important people, including her daughter the second Duchess of Marlborough; the architect of Blenheim Palace, John Vanbrugh; prime minister Robert Walpole; King George II; and his wife, Queen Caroline.

The money she inheritsfrom the Marlborough trust leaves her as one of the richest women in Europe.