The announcement was made at the conclusion of the 2018 Paris-Nice which was won by Movistar's Marc Soler ahead of Simon Yates (Mitchelton-Scott) and Gorka Izagirre (Bahrain-Merida).
It will be the second time the Mediterranean holiday town will play host to a Tour start with the first coming in 1981, the year Bernard Hinault claimed the third of his five career victories. Nice also last hosted a stage for the 100th edition of the Tour in 2013.
"The most recent editions of Paris-Nice (including the one that just finished yesterday) have shown us that the variety of landscapes and relief in this region are conducive to suspense, attacking and a thrilling spectacle," Tour de France race director Christian Prudhomme said.
"This is exactly what we want in order to give the Tour de France 2020 a dynamic tone. In Nice, we know that the pack and its support staff will be immersed for almost a week in a friendly atmosphere brimming with enthusiasm for cycling.
This year's Tour sets off from the Vendee in the west of France with the 2019 edition beginning in Brussels.