Alanna: The First Adventure, In the Hand of the Goddess, The Woman Who Rides Like A Man, Lioness Rampant
By Tamora Pierce [Pierce at LibraryThing — Pierce at Amazon]
Women in Tortall are not warriors, but 11-year-old Alanna would much rather become a knight than a lady or a sorceress — so she hatches a plan to trade places with her twin brother. Disguised as a boy named Alan, she enters training as a page, hoping to become a knight before she is discovered. As Alanna works to prove herself, learning both fighting and magic, she becomes friends with Prince Jonathan — and with George Cooper, a rogue who is the King of Thieves. But all of her friendships and new skills may not be enough when only Alanna realizes that the prince’s cousin, a powerful sorcerer himself, is plotting to take the throne to Tortall… And it seems like only Alanna will be able to stop him. (Very mild uncovered spoilers behind the cut.)