Mario Balotelli has pledged to win "much silverware for the fans" as he confirmed his move to Liverpool FC on his Facebook page.
He said: "I'm proud to announce my return to the Premier League as a Liverpool FC player. Let's make the most out of this amazing challenge ..."
He also uploaded a new banner photo of his face emblazoned on the Liverpool FC motto "you'll never walk alone".
Liverpool manager Brendan Rodgers has called the signing of Mario Balotelli "a smart piece of business."
Speaking to Liverpoolfc.com he said: "There is no doubting Mario's ability; he is a world-class talent and someone who, for such a young age, has vast experience of playing at the very highest level."
He added that he was looking forward to working with the "world class talent" and helping him progress as a player.
He said: "This transfer represents outstanding value for the club and I think we have done a really smart piece of business here."
Mario Balotelli has said he is "very happy" to be moving to Liverpool FC. In a statement on the club's website, he said:
I'm very happy. We've been talking about coming here and now I'm happy to be here.
Liverpool are one of the best teams here in England and the football is very good here.
It's a great team with young players, and that's why I came here.
Mario Balotelli has tweeted about his new club Liverpool FC shortly after the deal for his signature was completed.
YNWA! COME ON LIVERPOOL! ???
Liverpool have announced the signing of Italian striker Mario Balotelli shortly before they kick off against his former club Manchester city.
Steven Gerrard has backed Wayne Rooney to succeed him as England captain.Read the full story ›
Former Liverpool manager Graeme Souness has warned the club against signing Mario Balotelli, describing the move as an "enormous gamble".
AC Milan striker Balotelli is reportedly closing in on a transfer to Liverpool as Reds boss Brendan Rodgers looks to replace the goals of Luis Suarez, who joined Barcelona earlier this summer.
The #16million move for the controversial 24-year-old former Manchester City player is seen as something of a coup by many, but Souness believes it is a risk not worth taking.
Writing in the Sunday Times, he said: "It's an enormous gamble by Rodgers, a gamble I don't think he needs to take because he has a very strong group of players.
"The harmony looks good but he may find, like every previous manager of the Italian, that he will spend more time talking about Balotelli, spending time with him and defending him, than he will the rest of the group put together."
Souness, who managed Liverpool to FA Cup glory in 1992 and has also been in charge of Newcastle, Blackburn, Rangers and Southampton, went on to say that he would not sign Balotelli if he was still in the Anfield hotseat.
He added: "At times Balotelli doesn't seem to enjoy football. Big teams can do without people who pick and choose when they will have a go. It's a high-risk signing. I wouldn't want him."
Balotelli is a proven performer, but the baggage that comes with him is considerable.
His spell with Manchester City from summer 2010 to January 2013 was a whirlwind one, with occasional sparkling performances interspersed with volatility on the field and erratic behaviour off it.
He scored 30 goals in 80 appearances for the club and set up Sergio Aguero's stoppage-time goal against QPR which saw them crowned 2012 Barclays Premier League champions - their first league title since 1968.
Liverpool boss Brendan Rodgers has indicated he sees signing Mario Balotelli as a risk but one worth taking.Read the full story ›
In a press conference today, Reds manager Brendan Rodgers wouldn't talk about signing Mario Balotelli.
But he did say that he would never sign a player if he felt they would disrupt the atmosphere of the dressing room.
Talks between Mario Balotelli's representative and Liverpool are understood to be 'progressing well' as the club seek assurances about the player's behaviour - although any deal will not be completed in time for him to feature against Manchester City.
Reports have suggested the Reds have agreed a £16million fee with AC Milan for striker Balotelli's proposed move to Anfield.
And while Liverpool have not commented, Press Association Sport understands productive discussions involving Balotelli's agent and the club took place in England on Thursday and are continuing on Friday.
A key aspect of those discussions is believed to be the Merseyside outfit's desire to obtain some kind of guarantee about the discipline of the mercurial 24-year-old Italy international.
Balotelli himself remains in his homeland for now and will not be able to take part in Liverpool's Barclays Premier League clash with his former side City at the Etihad Stadium on Monday as the transfer would need to be completed by midday on Friday for him to be eligible.