OnlyFans model and combat veteran Joshua Hopkins spent part of his Bahamas vacation in jail -- dude got arrested for his role in a brawl at Nobu, and the whole fight is on video.

TMZ obtained footage of Joshua brawling with other patrons inside Nobu Bahamas on Paradise Island, and you see him landing punches and kicks ... but there's also a woman shattering a glass over Joshua's head!

The brawl went down right in the middle of Nobu's large dining room, in front of dozens of shocked guests and staff ... some even tried to break up the fight, to no avail.

Joshua tells TMZ he'd gone out to dinner with Jason Luv, a famous exotic dancer and porn star during their guys' trip to the Bahamas.

JH says as soon as they got to Nobu, people started coming up to Jason asking for photos -- all innocent enough. The trouble started when Jason went to the bathroom and Joshua alone at their table, noticed a couple staring at him.

Joshua says he made eye contact with them, and the woman suddenly stood up and yelled, "Who the f*** do you think you are?!?" He says her husband then stood up and got in his face, putting hands on Joshua ... and then all hell broke loose.

We mentioned the glass being smashed over Joshua's head in the fight video ... well, he says he suffered a cut that required treatment at a hospital.

While Joshua tells us he didn't want to press charges against the couple -- he thinks they were drunk and didn't want to ruin their vacation -- he says they pressed charges against him! So, cops showed up to his door the next day, and arrested him for assault and property damage.

Joshua says he spent 3 days in jail and had to pay an $800 fine because the couple claimed he ruined their clothing and sneakers during the melee.

As for Jason, who got some extra fame recently for banging Adam22's wife Lena The Plug, Joshua says his buddy was not involved in the fight -- he was actually at the front of the restaurant taking pics with fans when the brawl went down.