The King and Queen Consort have been thanked for a "generous donation" by the UK's Disasters Emergency Committee (DEC) which is helping earthquake survivors in Turkey and Syria.
The Prince and Princess of Wales also tweeted that they were supporting the appeal.
William and Kate said they were "horrified to see the harrowing images" in the aftermath of the earthquakes.
Funds will provide medical aid, shelter, food and water to thousands.
UK aid agencies - including the British Red Cross, Oxfam and ActionAid - are joining together to raise money.
The aid appeal was launched by the DEC and broadcast on TV on Thursday evening.
More than 20,000 people have died, with that number expected to rise.
The UK government has announced a support package to help survivors of the earthquake.
On Thursday evening a military plane will leave the UK, as Britain commits to sending equipment and staff to set up a field hospital with a 24/7 operating theatre.
Thousands of tents, thermal blankets and hygiene kits will be sent to the disaster zone.
The disaster has destroyed thousands of buildings have been destroyed and responders have been searching the rubble for survivors. Many people have lost homes, leaving them without shelter in freezing, wintry conditions, the DEC says.
In Syria, some people who were already living in tents after fleeing conflict in the country are now hosting those whose homes have been destroyed by the quake.
The charities say access to clean water is going to be difficult in the coming days, and waterborne diseases will be a hazard.
The UK government will match the first £5m of donations from the public. Money raised will also provide blankets, warm clothes and heaters for safe spaces.
The Scottish government is also contributing £500,000 and the Disasters Emergency Committee (DEC) Scotland officially launched its appeal on Thursday.
First Minister Nicola Sturgeon described the scenes in Turkey and Syria as "heart-wrenching", adding that: "This earthquake has caused a huge amount of damage and significant loss of life that will be felt for some time to come."
She said there was an urgent need to help the humanitarian efforts being made and emergency services had already been deployed.
The money donated to the DEC appeal would "support those affected with medical care, shelter, food and clean water", added Ms Sturgeon.
DEC chief executive Saleh Saeed described the scenes in Turkey and Syria as "heartbreaking", with thousands "losing loved ones suddenly in the most shocking of ways".
He said: "We know that money is tight for many people here in the UK as the cost of living crisis continues but, if you can, please do donate to support people caught up in this deadly disaster."
Mr Saeed told BBC Breakfast that DEC members had been working in Syria for 10 years because of the civil war which has engulfed the country.
"Despite the challenges they are all experiencing now... aid is getting through and they are scaling up," he said.
Salah Aboulgasem, from the Islamic Relief charity, based in Gaziantep, Turkey, added: "The priority right now is saving lives by clearing the rubble. The next priority is supporting people who have lost their homes and gone through huge trauma.
"People need medicines and warmth. There is a lot of screaming, people are trying to find relatives. A lot of people are sleeping in cars because they are scared to go back into the buildings due to aftershocks."
He later told BBC Breakfast that rescue teams were losing a "race against time" having gone passed the "critical" 72 hour-mark, but said there was "still hope" and "miracles are happening".
Dr Hans Kluge, World Health Organization regional director for Europe, told BBC Radio 4's Today programme that just 22% of people trapped in rubble survive 72 hours after an earthquake.
"Every minute counts now because the window to save lives is fast running out," he said.
Many in Turkey have been critical of their government's response to the crisis, while international aid has generally been slow to arrive.
Some 77 men and women from the UK International Search and Rescue, made up of firefighters and medics, arrived in Turkey on Wednesday afternoon and have already helped free people trapped under the rubble.
The DEC appeal was broadcast on the BBC, ITV, Channel 4, Channel 5 and Sky.
Fourteen of the DEC's 15 members are either responding, or planning to respond, in Turkey and Syria and will receive funds from the appeal.
The DEC has previously launched similar appeals to raise funds for victims of the Pakistan floods and for Ukrainians displaced by the war with Russia.
Watch: Earthquake rescues offer hope in Turkey and Syria