Athletic Club Bilbao won the Spanish Supercup after drawing the return leg of the final 1-1 at the Camp Nou Stadium.
Athletic continued their 4-0 win from the first leg on Friday night with a magnificent defensive display on Monday against a side which was aiming to win all six titles it could possibly win in 2015, Xinhua reported.
After Friday's defeat, Barca coach Luis Enrique fielded his strongest available side with Andres Iniesta, Sergio Busquets, Ivan Rakitic and Gerard Pique back on the pitch, while Claudio Bravo replacing Ter Stegen in goal.
Athletic, who travelled to Barcelona with five players injured, made just two changes in the squad, with Carlos Gurpegui and Eneko Boveda coming into the starting 11.
As expected after losing the first leg 4-0, Barca carried the weight in the first half and Pique was unfortunate to hit the bar after just seven minutes.
Iniesta and Pedro also went close, but for much of the first half Athletic were able to cope with the pressure and had their own chances through Aritz Aduriz and Javi Erraso.
Messi finally broke the deadlock after scoring from close range following a pass from Rakitic and a knockdown from Luis Suarez two minutes from the break to give Barca hope for the second half.
That proved to be false and Barca's hopes were reduced still further when Gerard Pique was sent off for apparently saying something to the referee 11 minutes after the break.
Athletic held on again in the second half and as both sides tired Aritz Aduriz, who had scored a hattrick in the first leg, netted for the visitors with eight minutes remaining to leave Barca needing to score five.
It is the first time Athletic have won in 31 years and a magnificent achievement for a club which only signs players born or raised in the Basque region of Spain.
