Three goals in the opening half hour saw the Blaugrana win the competition for a record 26th time, as Pep calls time on his four-year reign at Camp Nou in emotional fashion.
Winger Pedro scored two goals and Lionel Messi scored his 73rd goal of the season to give Guardiola one last trophy to celebrate as he departs the club.
In a repeat of the 2009 final the opening goal came inside three minutes as Pedro put Barcelona ahead capitalizing on the team's breathtaking tempo.
Messi gave Athletic a early warning as he was able to run at the opposition defense before putting his shot narrowly wide, before Adriano crossed for Pedro whose shot was deflected behind for a corner. The Catalans opted to swing the delivery in, and it reaped rewards when the ball fell to Pedro who reacted first to open the scoring.
The Basques looked to retain possession in the hope of building a sustained period of pressure on Jose Pinto's goal, but despite the keepers nervous clearances Athletic never truly threatened.
Barca continued to exploit the openness of Athletic's defense as Messi cut inside from the right before bending a goal-bound effort toward the top corner. But for Gorka Iraizoz's flying save, Marcelo Bielsa's side would have fallen further behind.
The Argentine, however, was not to be denied a second time. Messi latched onto Andres Iniesta's perfectly weighted through ball, taking it into his path with the outside of his left foot before lifting it into the roof of the net with his right.
Pedro would double his tally and give Barcelona a commanding 3-0 lead after he curled a precise finish into the far corner, following Xavi's delicate lay off five minutes later.
The third goal appeared to awaken Athletic Bilbao as it threatened immediately after the restart with Markel Susaeta forcing Pinto into a smart save.
However, Bielsa's side could have conceded a fourth when Messi managed to evade the attentions of Fernando Amorebieta latching onto a long ball, the wily Argentine attempted a lob from inside the area but it lacked the sufficient height to beat Iraizoz.
Fernando Llorente, who had cut a lonesome figure in the attacking third for Athletic, was finally offered some support as the Basques found their passing rhythm. Iker Munian slid a pass through to Athletic's talisman striker who turned expertly beyond Gerard Pique before, with a clear sight of goal, falling to ground only to see his claims for a penalty waved away by the referee.
Bielsa made two changes at the break in the hope of overturning the three goal deficit in the second half, the Argentine coach introducing Inigo Perez and Ander Herrera.
The changes had an immediate impact on the game as the Basque began to prevent Barca from dominating possession and territory, and were even afforded the first chance of the second half. Substitute Herrera slid an inviting through ball to Ibai Gomez but his attempted lob over an onrushing Pinto dropped beyond the target.
As the second half progressed the Catalans appeared to be content with their three goal lead as Athletic's chances were limited to set pieces.
With the contest seemingly over Guardiola's side appeared to be content with their three-goal lead as Athletic failed to create an opening. In fact Barca continued to look the more likely as they broke away, with Pedro denied a hat-trick thanks to a last-ditch tackle.
Xavi, one of the players to symbolize Barca as a club, was then given a resounding exit by Guardiola as the Catalan's looked to stroll to a comfortable finish.
The win, a 14th trophy for Guardiola in four years, cemented his place as the most successful Barcelona coach as he brings his legacy to a close, leaving the reigns to Tito Vilanova.