The UN says it will need a record $16bn (£10.5bn; 13.3bn euros) to fund its humanitarian operations next year, with almost half the total going to help victims of the Syrian conflict.
It says the money will provide aid for more than 57 million of the most vulnerable people around the world.
The UN humanitarian chief said the level of need was “unprecedented”.
The request comes as aid agencies warn they are running out of cash to fund this year’s operations in Syria.
Last week the World Food Programme announced it would have to cut food rations to Syrian refugees.
The UN is requesting $2.8bn to help those displaced by the conflict inside Syria.
It is seeking another $4.4bn to help more than 3,250,000 Syrian refugees registered in neighbouring countries.
“The rising scale of need is outpacing our capacity to respond,” said UN Undersecretary-General for Humanitarian Affairs Valerie Amos. “The crises in Central African Republic, Iraq, South Sudan and Syria will remain top humanitarian priorities next year.”
Ms Amos said those conflicts accounted for more than 70% of the funding being sought.