The contract extension will see the batsman remain with Northants until the end of the 2019 season.
Academy graduate Newton was first spotted by Ripley at the age of 12.
He has gone on to become a key member of the Championship squad, scoring 643 runs in eight appearances this year.
Newton also carried his good form into the Royal London One-Day Cup campaign, racking up 226 runs in six appearances.
And Ripley said: “I’m delighted to see Rob sign a new deal.
“He is an Academy graduate and now an experienced capped player.
“He has become a banker in Championship but has also added a lot to his white-ball cricket with a very strong 50-over campaign this year.
Newton is happy to remain with Northants for the foreseeable future.
And the 27-year-old said: “I’ve been here since I was 13 so it’s great to be able to continue my career with Northants.
“We are a strong, tight-knit squad and I’m keen to do my bit to help us push for promotion in the County Championship and hopefully win another white-ball trophy.”