Tufa, 28, scored a stunning upset with a great burst of speed over the last three miles to beat twice winner Keitany.
Tufa finished sixth at the worlds and third in the New York City Marathon, which Keitany won, last November.
"Winning in London was the greatest moment in my career so far," Tufa said in a statement issued by the organisers.
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"I am happy to be returning to London to defend my title."
Keitany is set to be Tufa’s strongest foe again and is the fastest woman on the start list with a personal best and African record time of 2 hours 18 minutes 37 seconds.
(Reporting by Mike Collett, editing by Pritha Sarkar)
