The 30-year-old returns to St. James’ Park eight-and-a-half years after he left his boyhood club, and has signed an initial one-year deal.
Carroll – who scored 33 goals during his first spell with the club – becomes head coach Steve Bruce’s fifth addition of the summer, following the arrivals of Joelinton, Allan Saint-Maximin, Jetro Willems and Emil Krafth.
"It feels very good. My friends and family are here, and it's the club that I support – it is home," said Carroll. "I enjoyed the time I spent here, and hopefully I can carry on where I left off. When I left eight-and-a-half years ago, I was scoring goals and I was enjoying my football. It's been a pretty tough time since then, and I just want to get back to that.
"I know it's home. I've played here, I've spoken to the fans - I am a fan - and my family is here. For me to get back to where I was, I think this is the only place for me."
Bruce said: "To bring a local hero like Andy back to Newcastle United is fantastic. He is very excited to be home.
"He is a big, physical threat in the opposition box and another great option for us at the top end of the pitch.
"He gives us something different to what we already have and we’ll do our best to get him flying again."
Born in Gateshead, Carroll came through the ranks at United and graduated from the club's Academy before making his senior debut in November 2006 at the age of 17 in a UEFA Cup win over Palermo - and becoming the club's youngest-ever debutant in European competition in the process.
After a loan spell at Preston North End, he was a key part of Newcastle's Championship title-winning side of 2009/10, netting 19 goals in all competitions and earning a place in the PFA Championship Team of the Year as Chris Hughton's side secured an immediate return to the Premier League.
In the summer of 2010 Carroll was handed the coveted number nine shirt and bagged 13 goals in 16 games for the Magpies, earning a full England debut against France in November 2010 before joining Liverpool two months later.
He won the 2012 League Cup during his time at Anfield, where he scored 11 goals in 58 outings, and was part of England's squad at the European Championships that summer - where he notched his first competitive goal for the Three Lions in their 3-2 group stage victory over Sweden.
A loan move to West Ham was made permanent in 2013, and Carroll - who has nine caps for his country - went on to net 34 goals in 142 games for the Hammers before departing earlier this summer ahead of his transfer deadline day return to Tyneside.
