Centrepoint said thousands of people aged 16 to 25 in England could find themselves sleeping rough or "sofa surfing" around the festive period this year.
The youth homelessness charity said the "worrying" figure could fill Leeds Arena one and a half times over.
Its survey of 227 young people who have been homeless found that 69 per cent felt that no-one cared for their wellbeing, while 72 per cent said it had a negative impact on their mental health.
Centrepoint's survey found that 33 per cent of young homeless people had spent a night in a park, 27 per cent had slept in a tent and 10 per cent stayed on a night bus because they had nowhere else to stay.
Almost three quarters of those surveyed also said they had "sofa-surfed".
Centrepoint chief executive officer Seyi Obakin said: "In the last 50 years, thanks to our supporters, Centrepoint has been there for thousands of young people when they had nowhere else to turn.
"However, for every person we reach, there are hundreds more who need support."
Centrepoint said it estimates that 22,250 young people will be at risk of homelessness between November 2019 and January 2020 based on data provided by 248 local authorities - 76 per cent of all councils in England.
The Ministry of Housing, Communities and Local Government said its Homelessness Reduction Act, introduced in April 2018, means that local authorities and other public bodies are working together to actively prevent homelessness for people at risk.
The ministry said its rough sleeping initiative has also provided £76 million to 244 councils to reduce rough sleeping.