The defender has joined the Magpies on a five-year deal.
Grant Hanley has voiced his delight at becoming Newcastle United's sixth signing of the summer, telling the club's official website that he simply could not turn down the opportunity to move to St. James' Park.
The Magpies' interest in Hanley had been widely publicised for the last few weeks, and Rafael Benitez has finally got his man after a third offer of around £5.5 million was accepted by Blackburn Rovers.
The former Rovers captain has signed a five-year deal with the relegated club to join fellow defensive recruits Isaac Hayden and Jesus Gamez on Tyneside.
The 24-year-old could not hide his delight at the deal when speaking to nufc.co.uk after signing, and admitted that it was impossible to resist the lure of pulling on the black-and-white shirt.
Hanley said: "I'm over the moon and delighted to be here. It is a fantastic opportunity to come and play at such a big club and one that I couldn't turn down.
"It is an exciting step in my career but it doesn't stop there. This is just the start and I am looking forward to helping Newcastle get back into the Premier League."
The Scotland international brings with him several seasons of Championship experience, and will be looking to nail down a regular place in the heart of Benitez's defence this term.
He will have to compete with fellow new signing Hayden, Kevin Mbabu, and the pair who finished last season as first choice, Jamaal Lascelles and Chancel Mbemba.