Using Facebook and Twitter has become the main way for young people to get news for the first time.
A study of 50,000 people by Reuters Institute for the Study of Journalism found that television had dropped to second place as young people's main source of news.
Of the young people surveyed between the age of 18 and 24, 28% used social media as their main source of news, whilst 24% used television.
The study found half (51%) of online users said they used social media as a news source.
Facebook took most of that share, with 44% of online users across 26 countries using the social media site to read, watch, share and comment on news, more than double its nearest rival YouTube on 19% and well above Twitter on 10%.
The fifth edition of the institute's Digital News Report spelled bad news for traditional news outlets: the survey found users noticed the original news brand behind social media content less than half the time.
The report said the rise of social media platforms for consuming news and the move to mobile was "undermining" the business models of publishers of quality news.
Reuters Institute director of research Rasmus Kleis Nielsen said: "As people increasingly access news via third party platforms, it will become harder and harder for most publishers to stand out from the crowd, connect directly with users, and make money.
"This development will leave some winners, and many losers."
In the UK, the number of people who said they were using their mobiles to access news rose from 42% to 46%, with 16% using it first thing in the morning.
Lead author Nic Newman said: "The move to smartphone goes hand-in-hand with the move to distributed content. Mobile users increasingly find news coming to them through social media feeds, alerts and notifications."
Traditional newspaper brands still lead the way in producing most of the digital content, followed by broadcasters and digital sites such as Buzzfeed and the Huffington Post, the institute said.