Despite a race-long duel with pole-sitter Daniel Ricciardo, Hamilton was able to make one stop less than the rest of the field, choosing instead to run his extreme wet tyres for much longer and swap straight to slicks rather than run the intermediates in between.
The decision gave him track position on Ricciardo, and despite the Red Bull at times being much faster than the Mercedes, Hamilton was able to keep the charging Australian at bay to take his first race win of the season.
Hamilton's day would only get better, too, when championship leader Nico Rosberg was passed on the run to the line by Nico Hulkenberg, meaning the German could only manage an eighth-[place finish that sees him concede 21 points to his Mercedes team-mate.
"I am kind of lost for words," Hamilton said after receiving the trophy from Prince Albert II of Monaco. "I prayed for a day like this and it came through. I feel truly blessed."
Ricciardo was disconsolate after the race though, and refused to join Hamilton and Force India's Sergio Perez in celebration due to what he saw as a second costly team error in as many races.
"The race shouldn’t have been as exciting as it was, to be honest," he said. "Two weekends in a row now I have been screwed. It sucks. It hurts."
Asked why there were no tyres at his second stop, he added: "I have no idea. I was called into the box. I didn’t make the call. They should have been ready."
With Monte Carlo experiencing monsoon conditions all morning - enough to see the supporting Porsche race red flagged before the final lap - FIA Formula One race director Charlie Whiting deemed conditions too difficult to start the race without the help of the safety car, with Fernando Alonso confirming before the race that the problem was not the level of standing water but rather the lack of grip given the track is a public road for the rest of the year.
No end to the drama
Despite the race starting as a procession, there was still no end of drama. Daniil Kvyat, in the Toro Rosso after his demotion from Red Bull ahead of the Spanish Grand Prix, pulled off the grid stuck in constant speed with the speed limited activated. He pitted to change steering wheel, but the Toro Rosso team were unable to cure the problem and he immediately lost a lap in the pits.
After seven laps behind the safety car and messages from Hamilton and Kevin Magnussen calling for the race to begin, the green flag came and Ricciardo led the field away. It lasted all of one corner, as the Renault of Jolyon Palmer ended up in the Saint Devote barrier after crashing in the star-finish straight.
As Palmer put his foot down, his rear wheels spun up on one of the zebra crossings and speared his car left into the barrier, leaving the former GP2 champion a passenger as he ran all the way to the tyre barrier at Turn 1, bringing out a virtual safety car period that lasted three laps to clear up the debris.
Raikkonen, Verstappen crash
The carnage continued as Kimi Raikkonen's poor weekend came to a premature end when the Ferrari driver slid into the barrier at the Loews Hairpin. Having ripped off his front wing and wedging it under his front-left wheel, the Finn had little control as he also forced off the Haas of Romain Grosjean, and despite trying to limp back to the pits he pulled off at the chicane.
It quickly emerged that Rosberg was holding up Hamilton with what was later revealed to be brake issues, and while the Mercedes' hindered each other, Ricciardo made hay and built a 13-second lead before Rosberg released Hamilton.
The three-times world champion went about trying to catch the Red Bull, but by now other cars were pitting for intermediate tyres. Ricciardo did likewise, but Hamilton decided not to and instead kept his wets on until the track was dry enough to go straight onto slicks.
Ricciardo pitted for a second time - this time for slicks - but any hopes he had of beating Hamilton out after a brilliant in-lap were dashed when he arrived to a pit box with no tyres ready for him. Ricciardo waited as the seconds ticked by, and as he returned to the track, Hamilton's Mercedes flashed pass and retook the lead by the slimmest of margins.
Ricciardo's team-mate Max Verstappen was backing up the genuine pace shown by the Red Bull all weekend, and despite a pre-race drama that required the entire front-left hub to be changed and starting from the pit lane following his qualifying crash, he charged into the top 10 to give himself a strong chance of points.
It all came to an end prematurely though when Verstappen locked up at the top of the hill and hit the outside wall at Massenet, while Magnussen also called it a day after tearing off his second front wing. With Verstappen's accident bringing out the second virtual safety car of the afternoon, a third was not far off.
The drama continues
Felipe Nasr had been given the shout - repeatedly - to let Marcus Ericcson through, but the Brazilian clearly had no intention of letting his Sauber team-mate by and forced the Swede to take matters into his own hands. Ericsson went steaming up the inside of the Rascasse Hairpin where there wasn't really a gap, and the two collided to cause significant damage that would lead to both retiring.
With a total of four restarts from virtual safety car periods, Ricciardo was able to get heat into his tyres much quicker than Hamilton and was able to challenge Hamilton for the lead. His biggest chance came when Hamilton straight-lined the chicane, getting his tyres wet and making a slow exit that allowed Ricciardo to have a run on the outside. Hamilton squeezed Ricciardo towards the wall, forcing the Red Bull driver to get off the throttle, and he waved his arm in frustration - though the stewards deemed it a legal move.
Ricciardo was clearly unimpressed by the move, asking "What the f*** was that?" on his radio before being told to keep cool by his Red Bull team, though the majority of the frustration stemmed from the error in the pit lane that would ultimately cost him victory.
Beyond that, Ricciardo dropped back, and all Hamilton had to do was maintain a calm head and see his ultra-soft tyres home to the finish after a mammoth 47-lap stint to close the gap to championship leader Rosberg to 26 points heading to Canada in two weeks' time.
MONACO GRAND PRIX RESULTS
1 Lewis Hamilton (Gbr) Mercedes GP 1hr 59mins 29.133secs
2 Daniel Ricciardo (Aus) Red Bull 1:59:36.385
3 Sergio Perez (Mex) Force India 1:59:42.958,
4 Sebastian Vettel (Ger) Ferrari 1:59:44.979
5 Fernando Alonso (Spa) McLaren 2:00:54.209
6 Nico Hulkenberg (Ger) Force India 2:01:02.132
7 Nico Rosberg (Ger) Mercedes GP 2:01:02.423
8 Carlos Sainz (Spa) Scuderia Toro Rosso at 1 lap
9 Jenson Button (Gbr) McLaren at 1 lap
10 Felipe Massa (Bra) Williams at 1 lap
11 Valtteri Bottas (Fin) Williams at 1 lap
12 Esteban Gutierrez (Mex) Haas F1 at 1 lap
13 Romain Grosjean (Fra) Haas F1 at 2 laps
14 Pascal Wehrlein (Ger) Manor Racing at 2 laps
15 Rio Haryanto (Ina) Manor Racing at 4 laps
16 Marcus Ericsson (Swe) Sauber-Ferrari 51 Laps completed
17 Felipe Nasr (Bra) Sauber-Ferrari 48 Laps completed
18 Max Verstappen (Ned) Red Bull 34 Laps completed
19 Kevin Magnussen (Den) Renault 32 Laps completed
20 Daniil Kvyat (Rus) Scuderia Toro Rosso 18 Laps completed
21 Kimi Raikkonen (Fin) Ferrari 10 Laps completed
22 Jolyon Palmer (Gbr) Renault 7 Laps completed
Original source: Hamilton's gamble pays off in Monaco