Farah followed up on the 10,000m title he won at the London 2012 Olympic Stadium seven days ago with a supremely calculated performance; the 29-year-old holding back in a race that started slowly before taking the lead with two laps to go and kicking on to finish in a time of 13min 41.66 sec.
Farah was pushed hard in the home straight by Ethiopa's Dejen Gebremeskel, who took the silver medal in 13:41.98, but held on to claim the Olympic tile over a distance in which he is already the world champion.
Kenya's Thomas Pkemei Longosiwa took the bronze medal in 13:42.36.
Just five men in Olympic history have previously taken the 5,000m and 10,000m titles at the same Games and Farah's win means the British team's medal tally has reached 60 – 27 gold, 15 silver and 18 bronze.
"It's just unbelievable," said Farah. "The American guy [Galen Rupp] tried to come past me, but I knew I just had to hold on to it. I had great support from the crowd. It means a lot to me."
"Those two medals are to my two girls that are coming. They're not born yet hopefully. They're twins so there's one for each. They could arrive any day."
Asked about his short-term future, Farah said: "I don't know what's going on. I'm taking one race at a time. The Olympics doesn't come round often. It's all worked out well. I'm just amazed. Two gold medals – who would have thought that?
"I just want to thank everyone who's supported me. All my coaches from previous years and all the people who've been involved in my life. I want to say particularly to my wife, with her carrying twins, it hasn't been easy but I didn't want to know about it."
He added: "It's been a long journey grafting and grafting, but anything is possible."
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