Mo Farah's career reached incredible new heights as the Briton became only the second man in history to complete an Olympic and world 'double-double' in the distance events.
The 30-year-old held on in a thrilling finish to add the 5,000m title to the 10,000m gold he won on Saturday.
It was a battle between Farah and Kenyan Isiah Kiplangat Koech down the home straight, with the Londoner moving away in the last 40m.
Farah crossed the line in 13 minutes and 26.99 seconds to claim his fifth global outdoor title.
"I never thought in my career I would achieve something like this," said Farah. "This was very tough - it was all left to the last two laps. I had a lot of pressure but at the same time I enjoy it.
"I am very proud to represent my country and hold the Union Jack. To all the people who give me great support I can't thank you enough. Thank you to all the people back home - I am very proud."
The historic feat in Moscow concludes an incredible 12 months for Britain's greatest distance runner, who has now matched the feats of Ethiopian Kenenisa Bekele.
Multiple world record holder Bekele claimed double gold at the Beijing Olympics in 2008 and repeated his exploits at the Berlin World Championships a year later to join his compatriot Haile Gebrselassie on the list of history's distance running greats.
Some will argue the absence of world records for Farah over the two distances is a hole in his glorious CV.
Farah, however, stands head and shoulders above his compatriots as the most decorated British athlete in history.
Before the start of these championships, Farah was level with triple jumper Jonathan Edwards and decathlete Daley Thompson with three major championship titles, but he moved above them in the space of a magnificent six days in the Russian capital.
BBC Sport commentator Brendan Foster called Farah the greatest British athlete of all time.
"For my money he is the greatest we've ever had," said Foster, who won bronze in the 10,000m at the 1976 Olympics.
"He put himself at the front and he would not let them past. Farah has always had challengers and he's always been able to hold them off.
"We are enjoying great times in distance running. Now we have a man who's inspiring the next generation of runners."
Five athletes in the field had faster personal bests than the 2011 5,000m world champion, and seven had gone quicker than him this season.
The race started at a slow pace which suited the Briton and with 600m remaining the double Olympic champion set off for the finishing line.
Farah could not entirely break free of Koech, but he was always in control and a final lap of 53.51 saw off the challengers.
He finished 0.28 seconds ahead of Ethiopia's Hagos Gebrhiwet, with Koech falling back to take the bronze.
BBC commentator Steve Cram, the 1500m world champion in 1983, said: "That was another incredible performance. His fifth global title - that's a fistful of gold.
"That was hard, really, really hard. It's not getting any easier, but it's just as sweet and just as brilliant. We are in special times with this special athlete."
Great Britain's men's 4x400m relay team were unable to make it a double celebration, though, as they had to settle for fourth place.
Nigel Levine was well placed going into the anchor leg but lost ground as a group of runners fought for position. He finished strongly down the home straight, but had left himself too much to do.