Regan \r(e)-gan\ as a girl's name (also used as boy's name Regan), is pronounced REE-gan, RAY-gun. It is of Gaelic origin. First used as a girl's name in the English-speaking world by Shakespeare as the name for one of the two disloyal princesses in his 1606 tragedy "King Lear". Also possibly surname used as a girl's name.
For more information, see also the related name Regina.