From Shakespeare's "Love's Labour's Lost." This character never has a name other than "Princess." She pays a visit to the King of Navarre and, along with some of her attendants, plays a game of wits with the King and his lords.
There are roughly one-sh*t billion tropes so PLEASE look through them before adding one. Otherwise add what you like. ADDITION: PLEASE read through the trope description provided before submitting something. It's not a huge deal but too often people submit characters that don't fit just because they misinterpreted the title...