It was a life out of a fairy tale — until it became one they couldn’t escape.

Sahar, Maha, Hala and Jawaher Al Saud are daughters of King Abdullah bin Abdulaziz, the Saudi Arabian monarch who is worth an estimated $15 billion.

With such riches, the sisters, when younger, would take ski trips to luxurious resorts in Europe and go on endless shopping sprees, buying silk robes and jasmine oil, while their doting father bought them parures — matching jewelry sets — topped with jewel-encrusted tiaras.

The women roamed elegant tents, filled with fresh fruits and treats, on an 85-acre, $740 million compound that included a helipad emblazoned with the king’s initials.

Each of them desired a normal, albeit privileged, life: to study abroad, travel the world, and eventually marry and have children.

Now they are prisoners.

Not only has the 89-year-old king forbidden any man to seek his daughters’ hands in marriage, he’s confined them, against their will, in separate dark and suffocating quarters at his palace.

The king’s eldest daughter, 42-year-old Sahar, spoke with The Post in a rare and surreptitious phone call.

“We are cut off and isolated and alone,” she says. “We are hostages. No one can come see us, and we can’t go see anyone. Our father is responsible and his sons, our half-brothers, are both culprits in this tragedy.”

Why are the princesses being held captive?

Because they believe women in Saudi Arabia, one of the most oppressive Islamic nations in the world, should be free. Their mother, Alanoud Al Fayez, long ago fled to London.

When the sisters openly spoke in opposition to women being illegally detained and placed in mental wards, the king had enough and no longer considered them his daughters.

“That was it for him. It was the end for us,” Sahar says.

“They once had a normal life for Saudi Arabia, but they are free thinkers, and their father hates that,” mom Al Fayez says. “They are compassionate about the plight of women in Saudi Arabia and throughout the Arab world. The injustices that we see are terrible, and someone must say something.”

Punished for having daughters

Al Fayez, a descendant of a well-to-do Jordanian family, recalls the first time she saw Abdullah. It was 1972. She was 15, he was 48, and she was told that he would be her husband.

“I was being given to him in marriage,” she says. “It was arranged.”

Despite the riches and the servants and the pampering, life quickly became “monotonous,” she says. Almost immediately, she got pregnant.

“After I was forced to marry him, Abdullah would come to my room as a visitor for a few hours every now and then,” Al Fayez says. “And then he’d go to his other wives, so you don’t even fight, you don’t even matter.”

The injustices that we see are terrible, and someone must say something. - Al Fayez

Within four years of the wedding, Al Fayez had given birth to four girls. This was unacceptable: She was, in the king’s eyes, incapable of producing a son, and so she was worthless.

Abdullah, who has had 30 wives and fathered more than 40 children, finally divorced Al Fayez sometime in the 1980s — but she didn’t find out until two years later, through an intermediary. In Saudi Arabia, a husband can divorce his wife without her knowledge.

“Really, he had divorced me a number of times and he’d abuse me, beat me and had me beaten by guards,” Al Fayez says. “And the more I took the abuse, the more I was abused.”

“The last straw, if you want to call it a last straw, really was that when my daughters got real sick, they wouldn’t let me supervise their care or participate in soothing them in any way.

“So that sparked my desire to break away and get to the West and tell the world about the abuses of women in Saudi Arabia.”

When it comes to the rights of women, Saudi Arabia has one of the worst human-rights records in the world. Women don’t have a say in raising their children. They can’t go to school, travel, open a bank account, conduct any kind of business or get medical treatment — especially gynecological surgery — without male permission.

In public, everything except the eyes and the hands must be covered, and the slightest infraction can result in a death sentence.

With the help of one of Abdullah’s security guards, Al Fayez fled the compound in the dark of night to Jeddah airport, where, with the help of a women’s rights group, she eventually flew to London.

It was an agonizing decision. Al Fayez says she would have fled with her daughters, but Abdullah had already confiscated the women’s passports and separated them from Al Fayez.

She also said she thought he’d eventually release them to spare the embarrassment of Al Fayez going public with her charges. At the very least, she thought their lives would be better than hers — that he would not mistreat his own children.

“Leaving my daughters was very difficult, but I never thought they’d be subjected to this,” she says. “After all, they are [the king’s] daughters too.”

Prisoners in his home

Al Fayez was wrong.

In 2002, less than one year after her escape, Abdullah began tormenting his daughters. They are in intermittent phone contact with their mother and have told her that he’s drugged their food and water to keep them docile.

“They had felt some oppression before I left, but when he found that I had gone, he vowed that he would kill the girls, slowly,” Al Fayez says. “At one point, he tried to get me to come back, saying that he would take away the divorce and release them, but that wasn’t true and I know that I couldn’t do it. I couldn’t trust that.”

It was then, about 2005, that she first began to fear for her daughters’ safety, she said. “That’s when I thought, now he’d do anything, even punish them till they die, which is exactly what he’s trying to do now.”

The king locked Sahar and the youngest, Jawaher, now 38, in one area of the palace, while confining Mahar, 41, and Hala, 39, to yet another closet-size and unkempt room.

Doctors aren’t even allowed in for checkups.

“The rooms they are locked in are so hot, they wilt from the desert heat,” Al Fayez says. They suffer from dehydration, nausea and heat stroke.

Her daughter Sahar says the king is starving them all to death. They haven’t had a full meal in more than a month, she says, and are forced to eat canned goods that they pry open with nail files.

“We are not angels dropped from the sky as a gift to our father,” Sahar says, “but I assure you that we didn’t commit a crime or do anything to deserve this.”

She was, in the king’s eyes, incapable of producing a son, and so she was worthless.

Power, running water and electricity are shut off at random, sometimes for days or even weeks at a time. Their rooms are overrun with bugs and rodents.

“Our energy is quite low, and we’re trying our best to survive,” Sahar says. Their “gilded cage” is only gilded on the outside. “We live amid ruins. You hear ‘palace,’ but we don’t feel like we’re in a palace at all.”

An official at the Saudi embassy in London tells The Post that the women are free to move about, but because they are royalty, they must be accompanied by armed security guards.

Al Fayez says that’s a lie.

“That place was once a home,” she says. “Now it’s a cage . . . The king wants them dead and he wants them to die in front of the world, yet he will deny any of this ever happened.”

All four women are routinely tortured, sometimes by their own relatives.

“They come in, the men, our own half-brothers, and they beat us with sticks,” Sahar says. “They yell at us and tell us we will die here.”

Marriage isn’t an escape

Each daughter, says their mother, once dreamed of marrying a prince. But with no chance to meet men on their own, and with their father indifferent, they remained single.

“He won’t let anyone take them in marriage, and he’s threatened to kill anyone who would ask,” Al Fayez says. “It’s about psychological warfare and breaking them down.”

Al Fayez said she feels every bit of her daughters’ pain, yet she tries to remind herself of how strong and special each of her girls is.

“Sahar is very bright and has always made us laugh. She’s the eldest, and she’s an artist and a free thinker,” Al Fayez says.

“Maha is sensitive but has a penchant for business and politics. Hala is compassionate and brilliant; she majored in psychology and graduated at the top of her class. She loves to play the piano and compose music. Jawaher, my youngest, is very similar in character to Maha. She also loves music and hopes to earn a degree in sound engineering.”

Her daughters, she says, have much to offer. She says she taught each of them to be strong, to stand up to their powerful father, and now that has backfired.

“My children have been living in agony,” Al Fayez says, “and this is far too great to bear. They are wasting away.”

Curiously, Abdullah has other daughters from other wives who are treated far, far better.

Princess Adila, for example, is married to a well-to-do Saudi businessman; she often speaks on behalf of her father. Abdullah appointed another daughter, Aliya, to the lead post in a Jeddah social-service program.

Princess Maryam, says Al Fayez, “is a doctor in Europe and she stays away.” The king’s youngest daughter, Sahab, 21, was given in marriage to Bahraini King Hamad bin Isa Al Khalifa in 2011.

Why are these four different?

“His hatred stems from their outspokenness,” Al Fayez says. “But from the beginning, even when he paid attention to them, he was angry that I didn’t give him sons. The fact that they are like me bothered him.”

We live amid ruins. You hear ‘palace,’ but we don’t feel like we’re in a palace at all. - Sahar

Al Fayez says she’s had little help in trying to secure her daughters’ release. She’s hired British and American lawyers, but Abdullah has refused to be questioned.

“We know that the daughters have gone for 30 days without any food or water,” says Ali Al-Ahmed, director of the human-rights group Institute for Gulf Affairs and a former Saudi political prisoner himself.

“They’ve been resourceful, putting away a little food here and there,” he says. “They are in survival mode.”

Sahar tells The Post that she’s constantly threatened by her father and has been told that death is the only way out.

“My father said that after his death, our brothers would continue to detain us and abuse us,” she says.

Al Fayez is frantic. Time, she says, is running out.

“My daughters want the right to see their mother, and I want to see my daughters,” Al Fayez says. “They are just trying to hold on to their sanity.

“They are suffering . . . with no hope for salvation.”