FIFA have confirmed that the 2026 World Cup will be the first to contain 48 teams. 
It will be the first tournament since France 98, to see an increase in participants. The World Cup in 1998, was the first to see 32 teams compete, and increase of eight from the 24 that took part at USA 94. 
Since 1998, the 32-team structure has remained intact, with two teams advancing to the Round of 16, from eight four-team groups. The current format will remain intact for the World Cups in Russia (2018) and Qatar (2022). 

Source: NNA