Published Monday, 17 December 2012
Ella Henderson is one of this year''s finalists (© ITV)
The 16-year-old made the announcement on Saturday when as she was performing on RTÉ's The Saturday Night Show.
She has beaten runners up Jahmene Douglas and boyband Union J in landing a lucrative record deal.
Thousands of fans have reacted on Twitter, sending the #EllaSignedtoSONY hashtag trending worldwide.
She confirmed the news on her account, where she thanked her fans for inspiring her music.
Ella made a shock exit from this year's X Factor competition, after she had been favourite to win.
The social media sphere went into overdrive when she was voted off during a sing-off - 48,000 tweets per minute were made during the sing-off between Ella and James Arthur.
Simon Cowell and Stephen Fry were among those who commented on the outcome, seeing the young singer booted out while controversial contenders Rylan Clark and Chris Maloney remained.
Her mentor Tulisa said the public had not voted to keep her because "people thought she was safe".
James Arthur, who won this year's X Factor, is currently number one in the iTunes chart with his single 'Impossible'.
The track also became the fastest selling single of the year so far, with 490,000 copies, according to the Official Chart Company.