A Straw Hat can refer to any brimmed hat that is woven out of straw. This hat is designed to protect the head from the sun, as well as protect against heatstroke. There are several styles of straw hats, but all of them are made of woven straw. Many of these hats are formed in a similar way to felt hats; they are softened by steam or by submersion in hot water, and then formed by hand or over a block. Finer and more expensive straw hats have a tighter and more consistent weave. Since it takes much more time to weave a larger hat than a smaller one, larger hats are more expensive.
Monkey D. LuffyEdit
In the One Piece series, Monkey D. Luffy's straw hat is the main symbol of the entire series and is the origin of his nickname "Straw Hat Luffy." His straw hat was given to him by his idol, Red Hair Shanks when he was a kid, and he promised to give the hat back to him once he becomes a great pirate (or in other words, the Pirate King). Much later, during the Straw Hat Pirates' departure for Fishman Island, it was revealed by Silvers Rayleigh that this straw hat originally belonged to Gol D. Roger.