The quartet boast just under 400 appearances and 25 seasons at Franklin’s Gardens between them.
And Saints boss Chris Boyd is delighted to have secured their services for the foreseeable future.
“We’re absolutely delighted to sign these boys on,” Boyd said.
“They’re four Saintsmen who’ve been here for a long time, and are all an important part of the fabric of our organisation.
“They’ve all played a good chunk for us, but a few of them are still young too and they’re all important cogs in our machine.
“We’re not completely finished in terms of our recruitment and retention, but we’re getting very close to getting the balance we want.”
Mallinder, a former ballboy at Franklin’s Gardens and Saints Academy product, made his club debut back in 2014.
But he really broke through between 2016 and 2018 where he became a fixture in the first team and earned a call-up to Eddie Jones’ England squad.
The versatile 23-year-old – who also previously captained England Under-18s and Under-20s – is equally comfortable at centre and fly-half, and is now back in first-team contention after missing most of the 2018/19 season through a serious knee injury.
“I think the club was good to Harry over the last 18 months and I think he’s been good to the club, too,” Boyd said.
“He’s done a lot of work for the Saints Foundation so he’s deeply entrenched in the fabric of Northampton Saints.
"This is home for Harry and we’re really pleased he’s staying on.”
Northampton-born Collins has been a fixture on the wing for Saints since Boyd’s arrival at the club, and is set to bring up a century of caps in black, green and gold this season.
The 25-year-old has notched up 29 Saints tries, 16 of which have come in the last 18 months, and Collins was the club’s second-highest try-scorer last season.
After representing England at U19 and U20 level, he initially broke into the Saints team during the 2013/14 season and was named the LV= breakthrough player of the season for his standout performances during the following campaign.
Boyd said: “He brings that little bit of X-factor; when you look at our highlights packages, you see how many times Tommy Collins is involved in those moments.
“When he’s hot, he’s very hot, and he’s a really valuable member of this team.”
Tighthead prop Hill arrived in Northampton from Yorkshire Carnegie back in 2015, immediately catching the eye of Jones and winning five caps for England in 2016.
Prior to his first Test cap for the Red Rose, Hill had represented his country at Under-17s, Under-18s, Under-19s and Under-20s level, taking part part in two Junior World Championship finals, including the 21-20 win over South Africa in 2014.
The 24-year-old enjoyed his most successful season in black, green and gold last term, making more starts than ever before and lifting the Premiership Rugby Cup before claiming his 100th club cap back in December against Leinster in Dublin.
“I’m really pleased for Hilly,” said Boyd. “He’s worked really hard to become an important part of our machine.
“He’s got a big future ahead of him and I’d like to see him stay at Saints for the next seven or eight years.
"If he does I can see him being both highly capped for the club and going on to play for England again.”
Tuala became a Saint back in 2015, initially joining the club as injury cover for Ben Foden before impressing the Franklin’s Gardens faithful with a stint in the No.15 jersey and making his deal permanent that summer.
The 30-year-old Samoa international scored the winning try in the 2017 European Champions Cup play-off final against Stade Francais, securing top-tier European rugby for the 2017/18 season in a fine finish to the campaign.
Tuala received the Saints’ supporters breakthrough player of the year award for his performances that term, and featured heavily the following two years with 55 appearances in all competitions and 14 tries.
And Boyd said: “Ace brings a lot of colour to our environment.
"He is highly skilful, brings a good, calming influence on the team, and he’s a good man to have on and off the field.”