Rapunzel is Disney's newest princess. Her movie is called Tangled, and has quite possibly one of the best Disney love songs, 'I See the Light'. She's delightfully kid-ish in personality, and is equally badass. Disney animators, you did a stellar job.
Rapunzel can be found in Magic Kingdom, in a 'play and greet' that replaced 'Storytime with Belle'. It's located on the walkway to the right of Cinderella's castle, if you're on your way to Cosmic Ray's or Fantasyland. Her lines are super long, so I only met her twice while I was there.
Rapunzel is paired with her prince, Flynn Rider.