The 25 year-old has been with Saints since arriving from Worcester in 2005 and has led them with aplomb since 2009, guiding them to consecutive appearances in the Aviva Premiership semi-finals as well as last season's Heineken Cup final.
Hartley said: "I'm delighted and very happy to be staying at the Saints. I've played all my professional rugby here, the club's a big part of my life and I'm happy to continue that."
Hartley has made 144 appearances for the Franklin's Gardens outfit, scoring 15 tries, and the increasing maturity he has showed has also seen him establish himself as an England regular.
The New Zealand-born forward has won 34 caps and started every game of England's Six Nations title success earlier this year, although the now-retired Steve Thompson was Martin Johnson's first choice during the Red Rose's awful World Cup campaign.
And with another three seasons lying ahead of him in the east Midlands, Hartley is keen to build on the success he has already experienced with Jim Mallinder's side.<!--[if !vml]--><!--[endif]-->