The elite showdown which closes the men's tennis season has been held in London since 2009.
"The five-year agreement will see the world's greatest players in men's professional tennis compete for the biggest indoor tennis title in the world at Turin's Pala Alpitour stadium, Italy's largest indoor sporting arena," the ATP said in a statement.
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Turin will be the 15th venue and the first in Italy to host the event introduced in 1970 as the biggest men's tennis tournament of the season after the four grand slams.
Manchester, Tokyo and Singapore were all competing to host the event, as was London, which hoped to continue welcoming the players to it's O2 Arena beyond 2020.
"Our congratulations to Turin on putting together such a comprehensive and impressive bid," said Chris Kermode, the ATP executive chairman and president, adding that the prize fund of 14.5 million dollars (13 million Euros) is a record for the Finals.
With six titles Roger Federer is the most successful ATP Finals player but last year's edition was won by rising German star Alexander Zverev, beating world number one Novak Djokovic in the November final.
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