The world body's Global Humanitarian Overview estimates that 168 million people worldwide will need some form of emergency assistance in 2020, including food, shelter and healthcare.
That figure marks a "record in the modern era," UN emergency relief coordinator Mark Lowcock told reporters, clarifying that he was referring to the period since World War II.
Needs continue to rise in part because "conflicts are becoming more protracted and intense," Lowcock said.
"Combatants display total disregard for humanitarian law," with the result that civilians caught up in conflict are increasingly likely to be displaced or traumatised psychologically, he said, adding that the number of attacks on schools and health facilities continues to rise.
In addition, climate change has unleashed more extreme weather events, notably drought and flooding, which trigger humanitarian emergencies, he said.
Millions will suffer in 2020
"The brutal truth is that 2020 will be difficult for millions of people," Lowcock said.
Of the 168 million people who are expected to require assistance next year, the 26 billion euro UN appeal is targeting the millions of people who are most in need and whom UN agencies are in a position to help.
The UN is seeking more than $3 billion to address humanitarian crises in Yemen and Syria, the countries most in need.
Venezuela is the country where needs have increased the most in the past year.
The UN sought nearly $740 million for Venezuela for 2019, but as the country's devastating economic and political crisis has intensified, that figure has risen to $1.35 billion.
