A golf fan had to spend a day in the hospital with a bloody head injury over the weekend … and it’s all ’cause Masters champ Hideki Matsuyama couldn’t keep a drive straight.

Here’s the deal … Matsuyama was competing in the 2021 Shriners Children’s Open in Las Vegas — when on the 16th hole of his second round on Friday, he cranked a drive that went way right.

You can see in footage of the shot, it was so far from the fairway, it accidentally crash-landed into a fan’s noggin — knocking the guy to the ground.

Robert, the fan who was hit, tells TMZ Sports he was a bloody mess after the ball drilled him … and felt “weird” and “totally disorientated.”

I was standing next to this guy when he got hit in the head by Matsuyama’s 300 yard drive. He took it like a champ! Hideki signed a hat and glove for him. The guy told Hideki not to worry about it and continue playing golf.

Robert says while he was trying to recover, Matsuyama was nice enough to sign an autograph for him and apologize — but the injury was so bad, Robert was eventually taken to the hospital.

injury was so bad, Robert was eventually taken to the hospital.

Robert tells us he needed 6 stitches to close the wound, and you can see in photos of the aftermath — the whole thing was gruesome.

Robert — who says PGA Tour officials have not reached out to him over the incident — has since started a GoFundMe to help with his medical bills, believing it could cost him in the $15,000 range.

He is expected to make a full recovery.

As for Matsuyama — who won the Masters in April — he finished the tournament in Vegas tied for 67th with a score of 4-under.