Barcelona's 3-0 win over Alaves on Saturday was their 10th consecutive opening day win in La Liga, breaking a league record which had stood since 1943.
Espanyol previously held the record with a run of nine straight wins on the first day of the Spanish top flight season between 1931 and 1943, either side of a break in play due to the Spanish Civil War.
Barca's win over Real Betis one year ago drew them level with their city rivals and their victory at the weekend moved them clear at the top.
The last time the La Liga champions lost on the opening day of a league campaign was 10 years ago in 2008, when Pep Guardiola's debut as the club's manager started with defeat against Numancia.
Since then, they have won each of their 10 curtain-raisers in La Liga, scoring 35 goals in the process and conceding just four.
Saturday's win over Alaves came courtesy of two goals from captain Lionel Messi and one from substitute Philippe Coutinho.
Barca have won seven of the last 10 league titles in Spain, including last year's under coach Ernesto Valverde, but Messi has named the Champions League as their main target this season.
Espanyol's nine wins in the 1930s and 1940s included success against Real Madrid and Barcelona twice before they were beaten by Castellon in 1934.