William II, Prince of Orange, married Mary Henrietta, the daughter of Charles I of England, on May 2, 1641 at the Chapel Royal of Whitehall. He was not quite sixteen, she was nine and a half. The painting was possibly done before the marriage, earlier in the year.
This was one of the last pictures Anthony van Dyck painted, maybe even the last. In January, or in summer, of that year, he traveled to Paris, where he fell seriously ill. In November, he returned hurriedly to London, where he died soon after in his house at Blackfriars. He was forty-two years old.