The UN head has urged Iraq's neighbours not to close their borders to refugees, and states further afield to do more to help tackle the humanitarian crisis.
About four million Iraqis live as refugees or internally displaced
Ban Ki-moon was speaking to a major UN conference in Geneva highlighting the plight of Iraqi refugees, which the UN says most countries have ignored.
The UN wants help for Syria and Jordan, which host 2m Iraqis, and for the US and EU to offer more refugees asylum.
It estimates up to 50,000 people flee the violence in Iraq each month.
There are up to four million Iraqis now living away from home, including 1.9m living as internally displaced people.
"I hope this conference will galvanise international support to provide them with more protection and assistance and I hope it will mobilise resources in establishing much needed protection space," Ban Ki-moon said in a video message.
He urged the international community to uphold the principle of no forced return to Iraq, which is in the grip of an insurgency and sectarian violence that claim dozens of lives a day.
Officials from more than 60 countries are attending the meeting which was called by the UN refugee agency.
The agency says many of the refugees and IDPs live in acute poverty with little access to health and education.
High Commissioner for Refugees Antonio Guterres says the international community has focused on the turmoil inside Iraq but neglected this dimension of the humanitarian crisis.
WHERE IRAQIS HAVE FLED TO
Gulf states: 200,000
Internally displaced: 1,900,000
"There is not enough attention on the fact that four million people have been displaced and they live in very, very difficult circumstances, some of them, both inside Iraq and outside Iraq.
"And the expression of international solidarity is absolutely crucial because, until now, let's be honest, they have been basically abandoned by us all," Mr Guterres said before the conference.
The UN wants commitments from wealthy countries, above all the US and EU, to support Jordan and Syria and to accept some of the most vulnerable refugees themselves.
Within Iraq many of the internally displaced people are sheltering with friends and relatives who have little space or food to share.
The agency says the refugee crisis in Iraq is the biggest population exodus since the displacement of the Palestinians following the creation of Israel in 1948.
The US-based group Human Rights Watch said the US and UK bore particular responsibility to help displaced people inside and outside Iraq.
"They undertook a war that has directly caused thousands of deaths, widespread fear and suffering, and forced displacement," said HRW refugee director Bill Frelick in a statement.
"This precipitated a sectarian conflict that has caused additional violence, persecution and displacement on a massive scale," he added.