The Prince of Wales will warn that "hatred and intolerance still lurk in the human heart" when he joins world leaders at an event marking the 75th anniversary of the liberation of Nazi concentration camp Auschwitz-Birkenau.
Charles has flown to Israel for the commemoration and in a speech will say that "language is used which turns disagreement into dehumanisation" and society must remain "resolute in resisting words and acts of violence".
His visit has added significance as the Queen has never made an official visit to Israel or the Occupied Palestinian Territories during her 67-year reign.
During his first day in the Holy Land, the prince will also meet Holocaust survivors and be joined by the UK's Chief Rabbi, Ephraim Mirvis.
He will deliver his address at the World Holocaust Forum being staged at Yad Vashem, the World Holocaust Remembrance Centre in Jerusalem, where guests are expected to include US Vice President Mike Pence, Russian President Vladimir Putin and French President Emmanuel Macron.
The prince has been invited to the major event by Israeli President Reuven Rivlin and he will meet the statesman as he begins his two-day visit to the Holy Land.
Charles will say in his speech: "The lessons of the Holocaust are searingly relevant to this day. Seventy-five years after the liberation of Auschwitz-Birkenau, hatred and intolerance still lurk in the human heart, still tell new lies, adopt new disguises, and still seek new victims.
"All too often, language is used which turns disagreement into dehumanisation. Words are used as badges of shame to mark others as enemies, to brand those who are different as somehow deviant.
"All too often, virtue seems to be sought through verbal violence. All too often, real violence ensues, and acts of unspeakable cruelty are still perpetrated around the world against people for reasons of their religion, their race or their beliefs.
"Knowing, as we do, the darkness to which such behaviour leads, we must be vigilant in discerning these ever-changing threats; we must be fearless in confronting falsehoods and resolute in resisting words and acts of violence. And we must never rest in seeking to create mutual understanding and respect."
Meanwhile, Polish President Andrzej Duda has refused to attend the event, complaining that he had not been allowed to address the audience, whereas Mr Putin and other leaders will speak.
Prime Minister Mateusz Morawiecki, attending the World Economic Forum in Davos, said the decision not to allow Mr Duda to speak was disrespectful to Poland.
"This is disrespect to Poland and to all the heroes of the Second World War who were saving Jews by not giving voice to the president of Poland. He should have been given (the) floor," he told the BBC.
"Had this been the case then of course Poland would have been represented. He was excluded from the speakers, which was offending."
Palestinian President Mahmoud Abbas has invited Charles to visit the Occupied Palestinian Territories and the prince will tour Bethlehem and sit down for talks with Mr Abbas.
Scott Furssedonn-Wood, Charles's deputy private secretary, said of the World Holocaust Forum: "The prince is honoured to be among the small number of international leaders who have been invited to address the event and have the opportunity on behalf of the United Kingdom to honour the memory of all those who were lost in the Holocaust."
While in the Middle East, Charles is also likely to pay his respects at the resting place of his grandmother, Princess Alice of Battenberg, in Jerusalem's Church of St Mary Magdalene.
She was honoured by the Jewish people for hiding and saving the lives of Jews in Nazi-occupied Athens during the Second World War.
The prince's visit - his first official tour of Israel and the Occupied Palestinian Territories - follows a similar visit made by his son, the Duke of Cambridge, who visited Israel and the Palestinian areas in 2018.
Charles has made previous trips to Israel, travelling to Jerusalem to attend the funerals of President Shimon Peres in 2016 and Prime Minister Yitzhak Rabin in 1995.
Holocaust Educational TrustChief Executive, Karen Pollock MBE, commented: "This year we mark the 75th anniversary of the end of the Second World War and liberation of concentration and death camps across Europe – a watershed historical moment.
"For survivors and for the wider community it means so much to see His Royal Highness leading the UK delegation to Yad Vashem for this distinguished gathering to reflect on the Holocaust and rising modern-day antisemitism.
"His presence sends a powerful message to the world – that this defining episode of our history should never be forgotten and be remembered for generations to come.”
Prince Charles: 'I have drawn inspiration from my dear grandmother, Princess Alice of Greece'
Charles finally got to the podium to deliver his speech at the World Holocaust Forum in Jerusalem around 90 minutes behind schedule after earlier events overran.
He told the invited guests that the stories of the Holocaust belonged to many of those in the hall and Jewish people across the globe.
He added: "But we must never forget that they are also our story: a story of incomprehensible inhumanity, from which all humanity can and must learn.
"For that an evil cannot be described does not mean that it cannot be defeated. That it cannot be fully understood does not mean that it cannot be overcome."
Charles highlighted the story of cellist Anita Lasker-Wallfisch, who survived Auschwitz and Bergen-Belsen before moving to Britain after the Second World War, and co-founded the English Chamber Orchestra, which the prince supports as patron.
He used the Hebrew for Holocaust - Shoah - when he added: "Just as each life lost in the Shoah stands for all the millions who died, each inspirational story such as that of Anita Lasker-Wallfisch stands for the strength of spirit, the unparalleled courage, the determined defiance, of the very best of humanity when confronted with the very worst."
He also spoke about the "immense pride" his family feels for Israel's formal recognition of the actions of the Duke of Edinburgh's mother, who provided refuge for a Jewish family during the war.
Charles was applauded after he said: "For my own part, I have long drawn inspiration from the selfless actions of my dear grandmother, Princess Alice of Greece, who in 1943, in Nazi-occupied Athens, saved a Jewish family by taking them into her home and hiding them."
President Reuven Rivlin: 'We are still expecting your mother to come'
Mr Rivlin welcomed the prince to his official Beit HaNassi residence in Jerusalem and told him Israel "deeply appreciates" his attendance at the forum, being staged at Yad Vashem - the World Holocaust Remembrance Centre in Jerusalem, which he said was aimed at fighting racism and fascism today as well as recalling the past.
Before the talks began, Mr Rivlin told Charles: "It starts with the Jewish people but we never know where it ends. Everyone needs to be very careful.
"With this gathering we show that when we are united we can fight this phenomenon."
The heir to the throne is the most senior royal to visit.
The Queen has never made an official trip to Israel or the Occupied Palestinian Territories and has not taken a long-haul flight for a number of years.
But Mr Rivlin said: "We are still expecting your mother to come."
The president recalled how he was born as a subject of Charles' grandfather King George VI, and how the British flag was replaced by the Israeli flag at the establishment of the state.
After almost 30 minutes of talks, Charles was given the rare honour of planting an English oak tree in the garden of the residence.
It comes 25 years after the Duke of Edinburgh also planted an oak in Israel in memory of his grandmother Princess Alice, who is recognised as Righteous Among the Nations at Yad Vashem for saving Jews during the Holocaust.
Chief Rabbi Ephraim Mirvis, in Israel for the day's engagements, joined the two world figures for the brief ceremony.
While the planting by Philip was a reminder of "deep sadness", the Chief Rabbi said, "This is a symbol of hope and represents the laudable aspiration you both have for sustainable development across the world".
He expressed hope it would "sow the seeds of peace" in the region and the world.
President Reuven Rivlin opens event with a speech
The World Holocaust Forum started almost 45 minutes late after an earlier event with Israeli Prime Minister Benjamin Netanyahu and Russia's President Vladimir Putin overran.
Israel's President Reuven Rivlin opened the event with a passionate speech telling the audience of around 40 world leaders: "Let us not be confused, anti-Semitism does not only stop with Jews.
"But racism and anti-Semitism is a malignant disease that dismantles people and states and countries and no society, no democracy is immune to that."
President Putin arrived about 30 minutes into the ceremony and after taking his seat was introduced to the Prince of Wales by Mr Rivlin, and the pair shook hands.