Published: 2017-09-10 10:40:54 BdST
The Argentine was handed a slice of luck with his first goal, which should have been ruled out for offside, and then showed no mercy to Espanyol, moving on to five goals in three league games as record signing Ousmane Dembele came off the bench in the second half to make his Barca debut.
Late goals from Gerard Pique and Luis Suarez completed the thrashing, with Dembele grabbing an assist, laying on the pass for the Uruguayan's goal.
Real, who were still missing talisman Cristiano Ronaldo through suspension, dropped points at home for the second game running as a misfiring Gareth Bale squandered a series of chances and Marcelo was sent off late on.
Elsewhere, Atletico Madrid were held to a goalless draw away to Valencia as they missed the presence of suspended striker Antoine Griezmann, while Sevilla warmed up for their Champions League trip to Liverpool by beating Eibar 3-0.
Soccer Football - Spanish La Liga Santander - Barcelona vs Espanyol - Barcelona, Spain - Sept 9, 2017 Barcelona’s Luis Suarez celebrates scoring their fifth goal with Ousmane Dembele and Andre Gomes. Reuters
The Argentine struck next from close range, sliding in to meet a Jordi Alba cutback 10 minutes before half-time after the Spain left-back had bombed forward on the break.
Messi completed his treble midway through the second half by finishing off a sweeping team move, lashing home another pass from Alba from inside the area.
"Despite the result it wasn't as easy as it looked. They (Espanyol) always play hard in these games and we came through a difficult game on top," said Barca coach Ernesto Valverde.
"They fought very hard, but we have players like Messi, who scored three goals, and Suarez, who gave everything, just like the rest of the team."
Espanyol have now lost on their last 10 visits to the Nou Camp and although they were grossly mismatched here they were still afforded a couple of chances, both falling to Pablo Piatti, who struck the post in the first half and narrowly missed the target with an attempted chip in the second.
In Madrid, Ivan "Ivi" Lopez gave Levante a shock lead in the 12th minute, flicking the ball into the air over Dani Carvajal as he tried to control a long throw-in and volleying into the near corner.
The Spanish forward came close to doubling the lead for the newly promoted side from a free kick which whistled past the near post, but Real levelled in the 36th minute when Lucas Vazquez tapped in from close range after Levante goalkeeper Raul Fernandez could only parry a header from Sergio Ramos.
Soccer Football - Spanish La Liga Santander - Barcelona vs Espanyol - Barcelona, Spain - Sept 9, 2017 Barcelona’s Gerard Pique scores their fourth goal. Reuters
"This is something we didn't want to happen. We have to learn from our errors and move on," said Real goalscorer Vazquez.
"We lacked a bit of freshness to create chances. Levante closed up very well at the back and caused us problems."
Levante goalkeeper Fernandez was in impressive form and his best save came from a low-struck effort from Marcelo, who in frustration rolled to the floor, kicking Levante's Jefferson Lerma and earning a straight red card in the 89th minute.
Bale missed a gilt-edged chance just before, while in injury time Toni Kroos came inches from a winner with an effort from the edge of the area which struck the outside of the far post.