The formidable Serbian, winner of 11 Grand Slam titles, had come into the tournament in superb form but Veselý, the current world number 55, signalled his intentions from the beginning by taking the first set.

Djokovic, who has won two of the past three editions of the tournament at the Monte Carlo Country Club, responded as he briefly found his form to level the match and sent the intriguing contest into a decider.

But the Czech player held firm as he regrouped in the third to wrap up a memorable 6-4, 2-6, 6-4 win and reach the third round.

The result handed Djokovic just his second defeat of the season and marked his earliest exit on the ATP World Tour in three years, after  he lost to Bulgaria’s Grigor Dimitrov at the Madrid Open.

Veselý will now go on to face either Paoli Lorenzi of Italy of France’s Gael Monfils in the next round.

“This is a proof nobody’s unbeatable,” said Djokovic.

“Happens so many times in my career that I lose a match - it’s not the first time.

“For me, there were just very few things I could take out from today’s match as a positive.

“I was playing really, really bad.

“But, taking nothing away from my opponent’s performance - he deserved to win.”

Djokovic’s shock demise has opened the door for the rest of the men’s singles field, with Spanish clay court specialist Rafael Nadal enduring no such problems as he comfortably saw off the challenge of British number two Aljaz Bedene.

Fourteen-time Grand Slam champion Nadal began his season on his preferred surface with a 6-3, 6-3 success against Bedene, who was born in Slovenia before he started to represent Britain last year.

The 29-year-old will face Austria’s Dominic Thiem in round three.

Fourth seed Stanislas Wawrinka, winner of the Monte Carlo Masters in 2014, is also through as he beat Germany’s Philipp Kohlschreiber in straight sets, 7-6, 7-5, and his next opponent will be French 15th seed Gilles Simon.