She is understood to have immediately requested asylum and filed for divorce from her husband.
But it has sparked a diplomatic crisis between Germany and the United Arab Emirates, where the Sheik is vice-president and prime minister as well as being the ruler of the city of Dubai.
He is said to have asked authorities in Berlin to return the princess, 45, son Zayed, seven, and daughter Al Jalila, 11, to the UAE, the Sun reports.
But they have refused and security officials are said to be protecting her.
Princess Haya is said to have told friends she chose to flee to Germany as she “didn’t trust UK authorities to hand her back”. The Sheik, 69, worth more than £9billion, is a keen racehorse owner.