Reigning champions Nigeria won 4-2 against Mexico, coming back from conceding the opener and then pulling away again after Mexico made it 2-2.
Mali also fought back from a goal down to earn a 3-1 victory over Belgium.
The African sides will go head-to-head for the trophy on Sunday at the Estadio Sausalito in Vina del Mar.
While Nigeria have booked their place in the final for the eighth time in 11 attempts, Mali’s teenagers are the first team at any age group from their country to reach a Fifa final.
They earned their place by responding superbly after falling behind to an early goal by Belgium’s Dante Rigo, hitting back with strikes by Boubacar Traore, Sidiki Maiga and Sekou Koita.
Nigeria’s semi-final with Mexico was a thrilling match, both sides giving their all and the Golden Eaglets finally coming out on top.
Mexico struck first through Kevin Magana but goals by Kelechi Nwakali and Orji Okwonkwo put Nigeria in front. The game swung again as Diego Cortes equalised but Nigeria responded and Osinachi Ebere made it 3-2 before Victor Osimhen sealed the win with a late penalty.
Osimhen’s strike was his ninth of the tournament and puts him joint-top of the all-time U-17 World Cup goalscoring charts alongside Ivorian Souleymane Coulibaly (2011) and Frenchman Florent Sinama Pongolle (2001).