It marks the first time in World Cup history that Spain have named a squad with no representatives from Los Merengues.
The reigning European champions are widely viewed as one of the favourites for the tournament, which will be staged across the United States, Mexico and Canada.
"The most critical process is scouting players, but the most painful part is leaving out players who are good enough to be there," said De la Fuente.
Spain are chasing a second World Cup crown after their triumph in South Africa in 2010, and De la Fuente recently identified his side among the leading contenders alongside two other nations.
Barcelona, fresh from winning the La Liga title, dominate the squad with eight players selected. Those called up from the Catalan club are Joan Garcia, Eric Garcia, Pau Cubarsi, Gavi, Pedri, Dani Olmo, Ferran Torres and Lamine Yamal. Marc Cucurella and goalkeeper David Raya were also included in the final squad.
Several notable names failed to make the cut, including Dean Huijsen, Dani Carvajal, Fermin Lopez and Fran Garcia. Lopez was ruled out after fracturing the fifth metatarsal in his right foot during Barcelona's 3-1 victory over Real Betis on May 17.
Spain have been drawn in Group H alongside Cape Verde, Saudi Arabia and Uruguay. Before the tournament begins, they will play warm-up friendlies against Iraq and Mexico.
Spain's 26-man squad for the 2026 World Cup
Goalkeepers: Unai Simon, David Raya, Joan Garcia
Defenders: Marc Cucurella, Alejandro Grimaldo, Pau Cubarsi, Aymeric Laporte, Marc Pubill, Eric Garcia, Marcos Llorente, Pedro Porro
Midfielders: Pedri, Fabian Ruiz, Martin Zubimendi, Gavi, Rodrigo Hernandez, Alex Baena, Mikel Merino, Mikel Oyarzabal
Forwards: Dani Olmo, Nico Williams, Yeremy Pino, Ferran Torres, Borja Iglesias, Víctor Munoz, Lamine Yamal
