Monkey D. Garp

Luffy's grandfather, the Marine vice-admiral called the Hero of the Marines.

Monkey D. Garp is a Marine vice-admiral in One Piece, the father of Monkey D. Dragon and the grandfather of Luffy, nicknamed Garp the "Fist" and the "Hero of the Marines".

Quick Facts

Affiliation: Marines
Rank: Vice-admiral
Family: Monkey D. Dragon (son), Monkey D. Luffy (grandson)

Facts from the source article.

Background

He is famous for cornering Gold Roger, and after Roger's execution he looked after Roger's son Ace, raising him as if he were his own grandson. His strength is enough to throw cannonballs like baseballs, and he can use all three types of Haki. He takes Koby and Helmeppo under his wing. After the war with Whitebeard he steps back from the front line to train the next generation of Marines. He is later imprisoned by Blackbeard on Fullalead after rescuing Koby there.