Madam Rolanda* Hooch
"Well, what are you waiting for? Everyone stand by a broomstick."
-- Madam Hooch
Madam Hooch is the Quidditch coach and flying instructor at Hogwarts. She referees the Quidditch matches between the House teams.
She is an expert on racing brooms and can be as enthusiastic as any of the older House team players are, and while admiring Harry's Firebolt, she mentioned that she first learned to fly on a Silver Arrow (PA13). This is the only hint we've had as to her age; the Silver Arrow was manufactured very early in the twentieth century before mass production was available (QA9).
*Madam Hooch's first name is given as "Rolanda" in the Trading Card Game. The Internet Movie Database website lists her first name as "Xiomara." Obviously they can't both be correct. Neither is considered canon until independently confirmed by JKR.
Harry Potter and the Philosopher's Stone: Madam Hooch is played by Zoë Wanamaker.