Kipyegon, 23, the silver medallist two year ago in Beijing, pulled away in the last 50 metres to clock four minutes 2.59 seconds for the gold medal, reports Xinhua news agency.
American Jennifer Simpson, who won the title in the 2011 Worlds and finished second in 2013, took silver in 4:02.76.
South Africa’s Caster Semenya, the 2009 world champion and twice Olympic gold medallist in the 800 metres, outplayed Britain’s Laura Muir and Sifan Hassan of the Netherlands, throwing herself at the line to take bronze.
An excited Kipyegon said after the race: “It was a good race in London. I knew it would be fast, it is such a quality field. The best was going to win here. It was always going to be quick and competitive.”
Simpson was satisified with a silver and said: “The last 300 metres in particular I ran my guts out and it paid off. Having the experience is huge because having the ability to stay calm is so hard, especially at the world championships when you’re racing in a beautiful stadium like this. To come out with a medal, I think it was down to keeping my wits about me.”
Semenya, who transferred to 1,500 metres from her more favourite 800 metres, was also jubilant with a bronze.
“I’m really happy with the bronze. Obviously a lot cannot go your way in a final, so to come out with a bronze is amazing, but I was hoping for a better time,” she said.
“1,500m is a tactical race, I tried to find my own space but fortunately I managed to get away with the bronze so I am happy,” she added.