The hosts essentially wrapped up all three points by half time as goals from Paco Alcacer and Lionel Messi capped off a mesmerising first-half display which also saw Barcelona hit the woodwork three times.
The second half did not live up to the first as Barca took their foot off the pedal, but there were few scares at the other end of the field as Ernesto Valverde claimed a routine victory over his former club.
The result takes Barcelona another step closer to a seventh title in the last 10 years, moving 11 points clear of second-placed Atletico Madrid and 18 above Real Madrid, both of whom are in action later on Sunday.
Messi opened the scoring after less than three minutes of the midweek Champions League win over Chelsea, and he came close to another early opener this afternoon when his fourth-minute free kick needed to be tipped over the crossbar by Kepa Arrizabalaga.
The hosts did break the deadlock after only eight minutes, though, as Jordi Alba's low pass into the box found an unmarked Alcacer, who made the most of his rare start in place of the suspended Luis Suarez by steering his finish into the bottom corner.
It was an ominous start for the visitors, and it looked likely to get significantly worse when Barcelona went pouring forward in search of a quickfire second, with Paulinho drawing a save from Kepa before Mikel San Jose was given a let-off by a rare heavy touch from Messi after losing possession in a dangerous area.
Messi then forced Kepa into a smart low save from 20 yards before breaking into a promising position again moments later, only for Kepa to deny him once more as he tried to sneak the ball in from a tight angle - much like he did against Thibaut Courtois on Wednesday night.
Kepa was well beaten just a minute later as Barcelona continued to have their own way, but this time the woodwork came to Athletic's rescue as Philippe Coutinho's brilliant first-time half-volley crashed off the underside of the crossbar.
It was one-way traffic for the hosts and Ousmane Dembele - who scored his first Barcelona goal in midweek - looked to get in on the act following some more scintillating football when Messi and Coutinho combined to find the Frenchman, who was denied by Kepa.
The second goal did finally arrive on the half-hour mark as Dembele turned provider, with his pass picking out Messi, who took a touch before drilling a clinical finish into the bottom corner from the edge of the area.
It was almost 3-0 just four minutes later when another devastating Barcelona move saw Paulinho clip a pass over the defence for Coutinho, but the Brazilian was again denied by the woodwork as he lifted the ball over Kepa and onto the top of the crossbar.
Athletic had the woodwork to thank for a third time in the first half when Paulinho struck it himself on the stroke of half time, with his curling effort clipping the outside of the post as the visitors found themselves fortunate and thankful to only be two down at the break.
Jose Angel Ziganda's side failed to register a single shot during the first half, but it took them less than a minute to correct that statistic after the restart when Inigo Lekue bundled through a challenge before dragging his finish wide of the target.
Indeed, it was a much improved performance from Athletic in the second half as Barca rarely got out of second gear, and Sabin Merino should have done better in the 51st minute when he failed to test Marc-Andre ter Stegen from a promising position.
It wasn't until shortly before the hour mark that Barcelona created their first sight of goal in the second half when Coutinho was played through down the left channel, but he could not squeeze his finish past Kepa from a difficult angle.
That was a rare moment of genuine attacking threat from the hosts in the second half, though, as they saw the game out having done their damage during a drastically contrasting first-half display.
Messi did look to light up the uneventful second period nine minutes from time when he cut inside onto his left foot, but his effort from the edge of the box was deflected into the arms of Kepa.
There was almost one more moment of Messi magic in the 88th minute as he carried the ball into the Athletic penalty area before working space to shoot, but this time he dragged his shot well wide of the target as Barcelona settled for the two-goal victory.
The result extends Barcelona's unbeaten run in La Liga to 36 matches - including all 29 so far this season - while they have not tasted defeat at home in the league since September 2016 - a run of 31 games.
Athletic, on the other hand, have now lost four La Liga away games on the bounce for the first time since August 2014 following a 14th successive defeat at Camp Nou.
BARCELONA (4-4-2): Ter Stegen; Roberto, Pique, Umtiti, Alba; Dembele (Iniesta, 64'), Paulinho, Rakitic, Coutinho (Gomes, 85'); Messi, Alcacer (Vidal, 74')
ATHLETIC BILBAO (4-2-3-1): Kepa; De Marcos, Nunez, Martinez, Saborit; San Jose, Benat (Iturraspe, 46'), Susaeta (Williams, 63'), Garcia, Lekue; Merino (Aduriz, 71')