McManus, 27, has been on loan at Northants since the start of the season, following the abrupt departure of former captain and wicketkeeper Adam Rossington. He has been a mainstay in the first XI, playing every game so far in the Championship and Vitality Blast.
“I’m delighted to sign on a permanent basis for Northamptonshire.” McManus said. “I’ve loved my time here so far this season and it’s a great club. I’m thoroughly enjoying playing alongside the lads and working with the coaching staff.
“I’m really excited about the next two years with Northamptonshire and to see where we can go and to challenge for silverware.”
McManus has averaged 29.28 in the Championship, with four half-centuries, with Northamptonshire sitting mid-table in Division One. On Sunday, he scored a century in a warm-up match against Bedfordshire, ahead of the start of the Royal London One-Day Cup.
“He’s been brilliant, an absolute true professional, a top man and one hell of a cricketer,” Northamptonshire’s head coach, John Sadler, said. “The lads have got a lot of respect for him and he’s going to play a big part for us moving forward.
“He’s an open-minded character that wants to learn, and continually improve. We know how good he is, and we know that he’s just going to keep getting better”.
“Coming into a new dressing room it can be hard to be vocal. But he’s grown and grown as he’s settled in, and since it was announced he would be here for the full season then he’s just become a natural leader behind the sticks. We can’t fault him, and we’re just delighted to have him on board.”
McManus came through at Hampshire, making his first-class debut in 2015, but had seen his chances of first-team cricket diminish with the arrival over the winter of Ben Brown from Sussex.
Hampshire’s director of cricket, Giles White said: “Lewis has been a fantastic servant to the club and an incredibly popular player; we will miss him. On behalf of everyone at the Hampshire I’d like to thank him for his contributions over the years and wish him the best with his move to Northamptonshire.”