After switching from Blackburn to Newcastle last summer, Hanley made just five league starts in 2016-17 as the Magpies won the Sky Bet Championship, and his only first-team involvement this term has been in the Carabao Cup.
Hanley arrives at Carrow Road with Norwich having shipped 15 goals in their opening seven games in all competitions this season under new boss Daniel Farke, including eight in their last two Championship outings.
Hanley told Norwich City TV: “Being able to come to a massive club and get games is a big motivation for me.
“It’s a club with high aspirations and a fresh start for me. As a defender, I’m a bit of an old-fashioned no-nonsense centre-half and you pride yourself on clean sheets.
“We’ve got work to do on the training ground to improve that so I’m looking to hit the ground running. I can’t wait to get started.”
Daniel Farke: "Grant is a quality defender and a leader too." #ncfc
— Norwich City FC (@NorwichCityFC) August 30, 2017
Farke said: “We’re really pleased to sign Grant because it is clear our defensive line needs strengthening.
“He is a quality defender with very solid experience and is a leader too. I really like his attitude and his desire to come and play for us as well as the attributes he will add on the pitch.”