Luke Procter has signed a three-year deal with Northamptonshire following a successful loan period at the end of last season.
Procter joins from Lancashire where he has spent the entirety of his career having graduated from Lancashire's Academy.
He topped the batting averages for Lancashire when they claimed the title in 2011, the season after making the first of his 66 first-class appearances for the club.
When he enjoyed the most prolific season of his career in 2016, scoring 822 runs with a career-best 137 against Hampshire, he had hopes that he had finally won a regular Championship place, but they did not materialise under the new coach Glen Chapple.
He shone for Northants with 82 and 94 in the County's final Championship match against Leicestershire at Grace Road - one which ended in disappointment when they won the match but narrowly failed to win promotion. He leaves with a year left on his Lancashire contract.
Procter said: "I'm really excited to have the opportunity to play for a club like Northamptonshire. They really impressed me at the end of last season whilst I was on loan and the lads have made me feel really welcome and part of the team."
Northamptonshire's head coach, David Ripley, added: "We really wanted to sign a batter that can bat time and build partnerships in red ball cricket. Luke showed in his time with us at the end of the season that he can do that job, averaging 58 and making three fifties.
"I am delighted he is joining us, he could have stayed in the squad at Lancs but he is hungry to play more cricket and is willing to move to get the opportunity. He is a more than handy fourth seamer too and his arrival will really sharpen the competition in the squad for starting places."