Daniil Medvedev reached his boiling point during his Australian Open match on Monday ... getting so pissed at a spectator, he told them to "f*** off."
The altercation went down as the Russian star faced off against Marcos Giron in the opening round of the tourney ... when he was up 5-2 over the American after winning the first two sets.
But, before Medvedev could handle business and finish Giron off, he confronted a fan in the stands for seemingly heckling him throughout the match.
As soon as he hurled the cuss word, the whole audience audibly reacted in shock.
The outburst resulted in a code violation ... which, naturally, Medvedev didn't agree with.
Eventually, Medvedev -- who's the 7th seed in the tournament -- was able to secure the win ... 6-0, 6-1, 6-2.
Medvedev's beef with Australian Open attendees has been well-documented over the years ... and he certainly hasn't shied away from letting his feelings known with umpires.
🗣 "Can you take control"
— Eurosport (@eurosport) January 11, 2023
Daniil Medvedev pleads with the umpire to take action against the crowd 🇦🇺 pic.twitter.com/fnb3R7MCMa
Medvedev's next match is against Australian John Millman on Tuesday ... and something tells us he won't be getting many cheers.