This is a hero hair braid as worn by Gerard Butler as King Leonidas in the epic Frank Miller's movie 300.
Braided in hair and tied with leather, this item was worn on screen by Gerard Butler. It is clearly visible in many moments in the film.
COA: Hollywood History
Image 2: Gerard Butler as King Leonidas on his battle outfit. You can clearly see this particular braid in this and many other scenes in the whole movie.