Paris Hilton's BF -- SHOVES FEMALE FAN at Cannes Film Festival

Paris Hilton's boyfriend lost his composure and aggressively pushed a female fan who got too close to the heiress in Cannes on Friday ... not once, but TWO TIMES, and it was all caught on tape.

The scene was utter mayhem -- Paris and River Viiperi were fighting through crowds of paparazzi to get into a party ... when one overzealous female fan got too close.

River -- clearly pissed off -- got physical with the woman and forcefully shoved her away ... but the lady kept coming back for more.

Paris finally snapped too and yelled at the woman to leave her alone -- but the woman didn't exactly comply.

Paris and River also went off on a security guard who tried to get handsy with Paris.