The expanded 32-team tournament is scheduled to take place in the USA next summer, with the competition set to run from June 15 to July 3.
The CONCACAF region have been given four spots for the 2021, 2022, 2023 and 2024 CONCACAF Champions Cup winners plus an invitational club of FIFA's choosing due to the fact the tournament will take place in the USA.
FIFA were widely expected to invite Inter Miami after the MLS franchise recently clinched the Supporters' Shield for the first time in their history.
Inter Miami to participate in FIFA Club World Cup
FIFA president Gianni Infantino confirmed Inter Miami's invitation following Saturday's 6-2 home win over the New England Revolution.
Messi came off the bench to score an 11-minute hat-trick to help Inter Miami break the MLS points record on the final day of the regular season.
Speaking during Inter Miami's celebrations, Infantino said: "We all know how Miami is in love with football and how Inter Miami is supported from across Florida and beyond for your exciting brand of football.
"Congratulations on your wonderful 2024 Supporters' Shield success. You have shown that in the United States, you are consistently the best club on the field of play.
"Therefore, I am proud to announce that as one of the best clubs in the world, you are deserved participants in the new FIFA Club World Cup 2025 as the host club representing the United States."
Could Messi face Guardiola at the FIFA Club World Cup?
As a result of FIFA's decision, Inter Miami will compete in the same competition as the likes of Bayern Munich, Chelsea and Juventus.
Messi could also face his former Barcelona manager Guardiola, who will take Man City to the USA for next year's tournament.
The pair won numerous trophies during their time at Barcelona together, including the 2009 and 2011 Club World Cups.
The Argentina international could also go up against one of his former clubs, Paris Saint-Germain, who are one of 12 European teams that will feature in the 2025 competition.
Unfortunately for Messi, there will be no Barcelona reunion after his former employers failed to secure qualification.
With Inter Miami confirmed for the Club World Cup, 31 of the 32 teams have now sealed their spot in the expanded tournament.
The final spot will go to the winner of the 2024 Copa Libertadores, with Atletico Mineiro, Botafogo, Penarol and River Plate all left in the competition, although the latter have already sealed their place for next summer's Club World Cup.