Some 12 million people around the world do not have citizenship of any country, and are being denied basic human rights as a result, the UN has warned.
The organisation is calling for more countries to sign up to two conventions on statelessness.
It says the issue is becoming worse as stateless children are born to stateless parents.
The problem is most widespread in South East Asia, Central Asia, Eastern Europe, the Middle East and Africa.
"These people are in desperate need of help because they live in a nightmarish legal limbo," said Antonio Guterres of the UN High Commissioner for Refugees (UNHCR).
"Apart from the misery caused to the people themselves, the effect of marginalising whole groups of people across generations creates great stress in the societies they live in and is sometimes a source of conflict."