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.
He 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 Isiah Kiplangat Koech down the home straight, with the Londoner easing away in the last 40m.
Farah crossed the line in 13 minutes 26.99 seconds to claim his fifth major championship 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.