A plan put forward by Gianni Infantino, head of soccer's world governing body, has been passed "unanimously" and the competition is due to expand from 32 teams to 48.
FIFA's Council discussed the options on Tuesday and rubber-stamped the move, which will come into effect in time for the 2026 World Cup.
So, what does the plan entail, and what does it mean for one of the most watched sporting events on earth?
CNN Sport takes a look at the detail.
What's the big idea?
Essentially, Infantino is keen to spread the love.
He wants the World Cup to be more "inclusive" -- and that means giving more of FIFA's 211 member associations the chance to take part in the tournament.
His predecessor Sepp Blatter held on to power for 17 years by appealing to regions outside the game's established power bases, and the Italian is using similar tactics.
Originally, Infantino envisaged a playoff round with the 16 winners going through to the main group stage and the losers going home after just one match.
But after a tweak to the plan FIFA now favors 16 groups of three teams, with the top two progressing to a last-32 knockout stage.
What happens currently?
Since 1998, when the World Cup expanded to accommodate 32 teams, the format has stayed the same.
There are eight groups of four teams, who all play each other once, with the top two progressing to the last 16. From there, it is a straight knockout format.
The last tournament, held in Brazil in 2014 and won by Germany, lasted just over a month. Any expanded tournament would mean more matches and almost certainly take longer.
Who made the decision?
The proposal was discussed by FIFA's Council at Tuesday's meeting in Zurich.
The council consists of 37 members, including the president, eight vice-presidents and 28 members elected by the national associations.
Infantino previously insisted the decision should be taken in the interests of developing football around the globe and should not be financially driven.
That said, a World Cup with 48 teams is anticipated to generate close to $1 billion in extra revenue, FIFA estimates.
Who is for and who is against?
Infantino said last month at a conference in Dubai that soccer federations around the world were "overwhelmingly in favor" of his proposals and those fringe countries who could benefit will surely be supportive.
And FIFA's bid to expand the competition got a boost when Manchester United manager Jose Mourinho said he was "totally in favor" of the idea.
The Portuguese, who has won titles in Portugal, England, Spain and Italy, says as a club manager, the fact there wouldn't be an increase in matches or a reduction in recovery time either side of the competition for players, is a big plus.
"The expansion means that the World Cup will be even more of an incredible social event. More countries, more investment in different countries in infrastructure, in youth football," he told FIFA's website.
There are some high-profile critics, though. Germany coach Joachim Low said he understood the eagerness from smaller nations but claimed the quality of football could suffer in the long run.
And last month, the organization that represents the biggest clubs in Europe registered its opposition to a 48-team World Cup.
The European Club Association has written to FIFA urging it to reconsider, saying the number of games played throughout the year is already at an "unacceptable" level.