The Whites, who sit 17th in the Premier League, find themselves in a relegation scrap with just four games left to play this season.
Advertisement
Leeds brought Gracia in as their replacement for Jesse Marsch in February, but following five matches without a win, he has been dismissed at Elland Road.
Between the pair, Michael Skubala took charge of three games, and now Allardyce takes the reins.
A statement read: "Leeds United can confirm Javi Gracia will leave the club after 12 games in charge.
Advertisement
"Zigor Aranalde, Mikel Antia and Juan Solla, who joined alongside Gracia, will also leave the club.
"We thank Javi and his team for their efforts under difficult circumstances.
"The remaining four games of the season will be overseen by experienced head coach Sam Allardyce."
Advertisement
Advertisement
Allardyce has managed over 500 Premier League games in a managerial career stretching 29 years and he brings a wealth of knowledge in fighting for survival, having guided a number of his previous clubs to safety.
Director of football Victor Orta has also left the club.
Allardyce, who was last in charge at West Brom in 2021, is the man tasked with keeping Leeds in the top flight of English football.
He spoke to talkSPORT on the morning of the confirmation.
Advertisement
"I'm stood here in my office overlooking the training ground, the fabulous facilities here at Leeds, excited to be involved again," he told White and Jordan.
"Obviously there's a tingle that runs through your veins when you take over a football club.
"I know it's in a lot of trouble. I've seen a lot of trouble before and hopefully - I could have done a little bit more time, but four games - hopefully we can make a difference and keep this fabulous club in the Premier League."
Advertisement
Asked what he thought of the opportunity, Allardyce added: "[I was] shocked, I never thought at this, at this stage of the season, there would be jobs offered.
"When the phone popped up with a name that I knew pretty well, I knew who it was straight away. So it took me about two seconds to say yes.
"Karl Robinson [joins]. And hopefully following will be another member of staff, maybe a bit more. We don't know yet, but certainly Karl at this moment in time."