Jon Rahm Drops Loud F-Bomb On Hot Mic During Open Championship

Jon Rahm's gonna have to wash his mouth out with soap ... 'cause the golf star was caught letting an expletive fly after a putt didn't go his way at the Open Championship on Friday -- passionately yelling out, "F***!!!"

The outburst happened on hole 10 in the second round as Rahm was looking to make par ... but things didn't go as planned, and he let everyone hear his frustration.

"Apologies for any language there," the announcer said shortly after the f-bomb.

The 28-year-old Spanish pro hasn't been the happiest of campers at the Royal Liverpool Golf Course this week ... voicing his frustrations over his play, as well as the amount of people surrounding him during the first round.

He even teed off on the media members who were following Rory McIlroy ... saying he had a "boom mic on my ass" as cameras kept up with his pairing partner.

The two-time major winner will have some work to do if he's looking to improve his spot in the standings ... he's currently tied for 49th at +2 through two rounds.