Marquise de Montespan
Mademoiselle Françoise de Rochechouart de Mortemart (are you still reading?) was born on 5 Oct. 1640. Through her marriage, she became the Marquise de Montespan. And this is the way she is referred to by historians.
The Marquise got to be one of the "official favorites" of Louis XIV for a period lasting over ten years, which is an excellent track record!
She also greatly contributed to the Sun King's descendance! He had six with the Queen and approximately seventeen (that we are aware of) with various mistresses... The Marquise de Montespan gave birth to seven of them! This makes her the most productive "official favourite"!