Denis Shapovalov just went scorched earth at the Italian Open -- the Canadian tennis star told fans in the stands to "shut the f*** up" in a fit of rage ... and the moment was captured on video.
The incident went down during Shapovalov's match against Lorenzo Sonego in the tourney's round of 64 ... when Denis got into an argument with the umpire on the sideline.
Denis was upset over a point penalty he received after crossing the net to show the ump a mark on the court .