The Catalan giants were already 3-0 ahead by the half-time whistle, with Robert Lewandowski scoring his 20th league goal of the campaign, while 19-year-old Alejandro Balde doubled their lead.
Lewandowski went on to score his second of the game, before Jules Kounde’s header made it 4-0.
Despite reducing the deficit through Javier Puado and Joselu, Espanyol remains in a precarious position near the bottom of the table.
With 12 points left to play for, Barcelona has a commanding 14-point lead over nearest rivals Real Madrid
This is their first League title since club legend Lionel Messi’s departure in August 2021 and their first under manager Xavi, who was appointed in November 2021.
Meanwhile, Espanyol faces the possibility of relegation from La Liga for the second time in four seasons, following their ninth defeat in 11 games, leaving them four points from safety with four matches remaining.