Real call Bernabeu news conference
Perez will appear at the Bernabeu stadium at 8pm local time, Real said on their website without giving further details.
The world's richest club by income, Real will end this season without major silverware following Friday's defeat by city rivals Atletico Madrid in the King's Cup final.
Portuguese Mourinho, who has done little to contradict reports he will return to Premier League club Chelsea next season, said it had been a "disastrous" campaign and his "worst ever" as a coach.
Paris Saint-Germain's boss Carlo Ancelotti has been widely tipped as Mourinho's successor and the Italian has told the French side he wants to leave.