The popular prop is leaving Worcester Warriors, who he joined from Saints back in 2017.
Waller came through the Academy at cinch Stadium at Franklin's Gardens, making 95 first-team appearances.
He made his debut for the black, green and gold in 2012 and became a regular in the squad during the club’s double-winning campaign of 2013/14.
Waller made 15 Premiership appearances during that stellar season and scooped Saints’ young player of the year award.
He has notched up more than 100 appearances since switching to Worcester, with only Exeter’s Alec Hepburn and Harlequins’ Joe Marler playing more minutes in the Gallagher Premiership at loosehead than Waller’s 2,301 since the start of 2020.
And now the 29-year-old is preparing to return to the club where he made his name.
Waller said: “I’m absolutely delighted to be returning to my hometown club at what is a really exciting time with Phil Dowson and Sam Vesty – two coaches I know well – taking the lead next season.
“I’ve loved my opportunity at Worcester and will be forever grateful for the chance they took on me, but now definitely feels like the right time to come home.
“I’m returning a better rugby player, a better bloke, and I’m really looking forward to being back at Franklin’s Gardens week in, week out.
“I have supported Saints since I was a kid, and so to run out in black, green and gold again will be a huge moment for me and my family.
"I’m focused on finishing the season strongly with Warriors but I’m excited to head back to Northampton this summer to hopefully help the team win some silverware in the years ahead.”
Between 2012 and 2017, Waller became a fans' favourite around cinch Stadium at Franklin’s Gardens – thanks not only to his eye-catching performances in the loose and anchoring Saints’ scrum, but also helping to set-up numerous fundraising events for charity.
He was elected chairman of the Rugby Players Association in 2021, succeeding Mark Lambert of Harlequins.
“We’re very pleased to see Ethan return to Franklin’s Gardens,” said Phil Dowson, who will take over as Saints boss this summer.
“He left the club in 2017 in search of more game time, and he’s gone to Worcester and cut his teeth playing a lot of Premiership matches.
“Ethan’s an excellent scrummager – which is essential – but his ability to get himself in good positions, carry and move the ball in the loose is really important in him being able to fit back into the way Saints play.
“Off the field, he’s a great man who I have a lot of respect for. We know he’s very much a player who will put Saints first with his attitude, and look to keep the group together.
“But most importantly, on the pitch Ethan’s a quality and robust player, who plays the game hard.
"We see him being able to make significant contributions for us on a regular basis.”