Sue Sim was the first woman to lead the force and led the hunt for murderer Raoul Moat in 2010.
Last month Northumbria Police and Crime Commissioner Vera Baird launched an investigation into Ms Sim over alleged rudeness to staff.
Ms Sim is retiring on 3 June to spend more time with her family to "make up for the sacrifices" they made.
She joined Merseyside Police in 1985, progressing through the ranks before moving to Northumbria in 2004.
Ms Sim said the hunt for Moat following the murder of Christopher Brown and shooting of one of her officers, PC David Rathband, was one of the biggest challenges she faced.
She said: "That was the largest manhunt the country has seen for 44 years. I spent my time out and about reassuring the public and responding to their questions.
"I am immensely proud of my officers and staff who went about their roles fully aware of the threats against them, but determined to support the public."
She has also overseen savings of Â£117m since 2010 and was at the helm as Northumbria Police reopened no crime rape reports following an audit.
Ms Baird's office said the misconduct investigation will continue but admitted if the complaints against her were upheld, Ms Sim's retirement would mean any sanctions, such as a written warning, would have no impact.
Ms Baird said: "Sue has brought passion and enthusiasm to her role and leaves at a time when Northumbria is one of the highest performing forces in the country."

The 46-year-old has been on the Premiership club's coaching staff since 2004, took over as head coach in 2009 and became director of rugby in 2010.
"It is with great sadness and regret that I leave my position. I still believe that I am the right person to lead the team," Cockerill said.
Head coach Aaron Mauger will take over on an interim basis.
Tigers are fifth in the Premiership, 15 points adrift of leaders Wasps having lost five of their 12 league games so far this season. The were beaten by 16-12 by Saracens on New Year's Day.
Cockerill, who has spent 23 of the last 25 years of his career with Tigers, said he "respected the board's decision" to make a change they see as being "in the best interests of the club".
He added: "This club has made me the person and the coach I am today and I will never forget what they have done for me. I will miss being part of the Tigers family."
Last month, following the 18-16 Champions Cup win over Munster, Cockerill said reports claiming he faced the sack and that described the coaching structure at Leicester Tigers as toxic were "rubbish".
Former England and Tigers hooker Cockerill spent 10 years with the club as a player from 1992 before returning to Welford Road as an academy coach.
After two spells in interim charge he was appointed full-time head coach in April 2009, with Tigers winning the Premiership title and reaching the European Cup final in his first season in the role.
Leicester have never failed to reach the Premiership semi-finals under Cockerill and as well as winning the final in 2008-09, they were also victorious in 2009-10 and 2012-13.
Tigers chairman Peter Tom CBE said: "We thank Richard for his loyal and dedicated service as a player, coach and director of rugby. He has a great passion for the club and for the game of rugby, and has shared in many massive occasions with the Tigers.
"The club always has aspirations to contest the major honours in the game and that remains unchanged but the board believes this is the right time to make a change."
As a player, hooker Cockerill made 262 appearances for Tigers, winning five league titles, two domestic cups, two Heineken Cups and he also played 27 times for England.
BBC Radio Leicester commentator and ex-Tigers fly-half Bleddyn Jones
I am not surprised. Tigers cannot stand the fact they are in fifth position and quite a bit away from the top four; they want to be top two and won't get there this season.
They haven't been there for the last three or four seasons and that is one of the reasons that Tigers have reluctantly had to say goodbye to Richard.
His record is second to none. He is man and boy with the Tigers and if you cut him in half he would be Tigers colours through and through.
The chief constable of Northumbria Police will retire after 30 years of service, it has been announced.
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Leicester Tigers have sacked director of rugby Richard Cockerill after nearly eight years in charge.