What episode does Luffy use Gear 4?

Monkey D. Luffy used his Gear 4: Boundman (aka Bounceman) for the first time in episode 726 of the One Piece anime in his battle against Donquixote Doflamingo, the Heavenly Demon.

The 'One Piece' Episodes Where Luffy Gets Each of His Gears, Explained

One Piece: All of Luffy's forms, explained

When will Luffy's Gear 5 be animated in One Piece?

One Piece Gear Fourth! Kyoui no Bounce Man! (TV Episode 2016) - IMDb

Luffy Use Gear 4 Tank Man for the First Time (60fps)

Gomu Gomu no Mi/Gear 3 Techniques, One Piece Wiki

Gomu Gomu no Mi/Gear 4 Techniques, One Piece Wiki

One Piece: 10 Amazing Facts Most Fans Don't Know About Gear Fourth

How many Gears does Luffy have in One Piece?