Espanyol have been relegated from LaLiga for the first time since they gained promotion in 1992-93.
The Catalan side suffered a 1-0 loss away to city rivals Barcelona on Wednesday night, their sixth defeat in a row, to seal their fate.
The loss left them rooted on 20th with 24 points from 35 matches — 11 points from safety with three matches to go.
Luis Suarez scored the all-important goal in 56th minute, three minutes after both sides were reduced to 10 men.
First, it was Fati Ansu who was shown the dreaded card five minutes after coming on as a substitute before Espanyol's Pol Lozano suffered a similar fate three minutes later.
It was also their 11th consecutive league defeat away to Barcelona at the Camp Nou Stadium.
In other results of the night, Villarreal kept alive their chances of playing in next season's Champions League as they beat Getafe 3-1 to close the gap on fourth-placed Sevilla.
After a goal-less first half, the match sprung into life in the last quarter, with Santi Carzola scoring a pair of penalties; on the 68th and 86th minute, sandwiching Hugo Duro's 80th-minute strike.
Ruben Pena then ensured victory for the Yellow Submarines with a 93rd-minute strike to open a four-point gap to sixth-placed Getafe.
Elsewhere, Real Betis secured its stay in the first division with a 3-0 win over midtable Osasuna to put an end to a three-match winless streak.