Daniil Medvedev Tells Fan To 'F*** Off' During Australian Open Match

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.