|Location(s)||Creepy Steeple, Merlee's Basement, Mansion Patrol, Vortex Island, Lighthouse Island|
|Tattle||"A somewhat shy ghost that can make itself or its allies invisible. It may be a ghost, but it's pretty cute". (Paper Mario TTYD, Tattle Log).|
|Catch Card #||092|
Boo is a recurring character in the Paper Mario series and in the Mario series in general. It is a ghost that, in most cases, is an enemy. However, in Paper Mario, the Boos live in Boo's Mansion and Gusty Gulch, and they are all friendly. In addition, in Paper Mario: The Thousand-Year Door, a few help Mario in the Creepy Steeple. They attack by scaring and can turn themselves invisible for one turn, as they are ghosts. Boos also have a relative called Dark Boos which are powerful purple Boos. In Creepy Steeple, they can team up and form the optional mini-boss Atomic Boo. In Super Paper Mario, Boos appear in Merlee's Basement and use a "Red Light, Green Light" move like they do in most Mario games - hide when seen. It is best to jump while they approach Mario and jump on top of them. Boos also appear in the Arcade minigame Mansion Patrol, where whomever is playing must shoot the Boos. Toads are sometimes held captive, but shooting a Boo will release him and a 1-Up/Power Up. In Paper Mario: Sticker Star, the Enigmansion has been overrun with Boos and it's up to Mario to put them back in their magic book Kamek released them from.
| Species: Boo | Dark Boo | Atomic Boo |
Characters: Lady Bow | Bootler | Peeka | Lahla