Real Madrid's game against Valencia, which was scheduled for Saturday night, was postponed due to the devastating floods in Spain, which meant that a win for Barcelona would have opened up a nine-point advantage over the reigning champions.
The hosts were simply irresistible in the opening half of action, with Dani Olmo netting twice, while Raphinha was also on the scoresheet, with Hansi Flick's side leading 3-0 at the break.
Olmo's first came after a brilliant pass from Lamine Yamal, before Raphinha lifted one over the onrushing Espanyol goalkeeper after Marc Casado had split the away side's defence with a clever pass.
Two became three in the 31st minute, and it was another super goal, as Olmo found the back of the net from outside the box, and Espanyol were simply unable to deal with the quality and movement from the runaway leaders.
Espanyol only had 23% of the possession in the opening half of action, with Barcelona looking every inch a team capable of reclaiming the title this season, and they have now scored an incredible 40 times in their first 12 games of the La Liga season.
The visitors did get their name on the scoresheet in the 63rd minute, with Javi Puado converting at the far post after Carlos Romero had delivered a dangerous cross into the penalty box.
However, the damage had been done in the first period, with Barcelona making it six straight wins in all competitions courtesy of a comfortable success in the Barcelona derby.
BARCELONA VS. ESPANYOL HIGHLIGHTS
Dani Olmo goal vs. Espanyol (12th min, Barcelona 1-0 Espanyol)
Barcelona make the breakthrough in the 12th minute of the contest, with Olmo turning into the back of the net from inside the box after Yamal had delivered a wonderful cross into the penalty box.
23rd min: Barcelona 2-0 Espanyol (Raphinha)
Barcelona double their advantage in the 23rd minute of the match, and it is a clever finish from Raphinha, as the Brazilian lifts the ball over the onrushing goalkeeper following a super pass from Casado.
31st min: Barcelona 3-0 Espanyol (Dani Olmo)
Barcelona have their third of the match in the 31st minute and surely secure all three points in the Barcelona derby, and it is a second of the match for Olmo, who drills one into the back of the net from outside the penalty box.
63rd min: Barcelona 3-1 Espanyol (Javi Puado)
Espanyol have a goal back here, as Puado turns in at the far post after Romero had delivered a dangerous cross into the penalty box. Could Espanyol launch a late comeback here?
MAN OF THE MATCH - DANI OLMO
Olmo has now scored five times in five La Liga appearances for Barcelona, with the Spain international coming up with a brace during the Catalan derby on Sunday afternoon, and Espanyol just could not deal with him.
The 26-year-old scored two excellent goals, while he also won three aerial duels during an excellent performance, but he was withdrawn early in the second period, having only just recovered from an injury.
BARCELONA VS. ESPANYOL MATCH STATS
Possession: Barcelona 77%-23% Espanyol
Shots: Barcelona 13-10 Espanyol
Shots on target: Barcelona 9-3 Espanyol
Corners: Barcelona 9-5 Espanyol
Fouls: Barcelona 13-14 Espanyol
BEST STATS
WHAT NEXT?
Barcelona will be aiming to make it seven straight wins in all competitions when they travel to Red Star Belgrade in the Champions League on Wednesday night, before visiting Real Soicedad in La Liga next Sunday.
Espanyol, meanwhile, will be bidding to bounce back from the defeat in the Catalan derby when they host Valencia next weekend in what is already a big match towards the bottom of the division.