The Atletico Madrid midfielder had the rumour mill turning earlier this week when he posted a cryptic message on social media that read "New club: I'll announce [it] in three days".
Manchester United have long been linked with a move for the Spain midfielder, while Chelsea, Arsenal, Paris Saint-Germain and Bayern Munich have also been among his reported suitors.
However, with six years to run on his Atletico contract and a reported €150million release clause, it always seemed a little unlikely Saul's news would be transfer-related.
And so it has proven to be, with the 25-year-old announcing the creation of Costa City Club along with his brother Aaron.
The structure of the Costa City project, which is being sponsored by Nike, will see teams comprised of boys and girls aged between four and 18.
Saul said: "We have been developing this exciting and beautiful project for several years and I am very happy to be able to present it and make it official today."
Atletico is due to return to LaLiga action following the suspension of top-flight football in Spain as a result of the coronavirus pandemic with an away fixture at Athletic Bilbao on 15 June.