François Mansart (23 January 1598 – 23 September 1666) was a French architect credited with introducing classicism into Baroque architecture of France. The Encyclopædia Britannica cites him as the most accomplished of 17th-century French architects whose works "are renowned for their high degree of refinement, subtlety, and elegance". Mansart, as he is generally known, popularized the mansard roof, a four-sided, double slope gambrel roof punctuated with windows on the steeper lower slope which created additional habitable space in the garrets.