The young defender verbally pledged his long-term future to Saints back in January, and has now followed suit by penning an extended deal on the day he turns 18.
Shaw's future has been the subject of much speculation, even since he publicly declared his intention to continue his development with Southampton.
The left-back has been with the Club since the age of eight, progressing through the Academy to make his debut for the First Team in an FA Cup game at Millwall in January 2012.
Since making his first league appearance for Saints last November, Shaw has been a regular in the team and now has 29 senior appearances to his name.
With his future now secured, Shaw's new contract will allow him to maintain his progress as the Club looks to realise its ambitions during the coming seasons.
"I'm very pleased to have finally signed it," said Luke this evening. "I committed myself back in January, and I'm glad everything has been sorted out.
"I've been getting a lot of questions about my future, but all of the Saints fans will have known that I committed my future in January.
"I've been here since I was eight and I've loved every single moment of it. I want to stay at this Club, and signing this contract means I'm here for another five years.
"The players, the staff, the medical team and the fitness coaches have all helped me come this far," he continued.
"You can see what the Chairman is trying to bring into Southampton. He's trying to build a young team for the future that will be very good.
"The manager has done a lot for me – especially for my fitness – and this year is going to be a big year for me.
"I've come back very, very fit and better than last season, so I can't wait to get started."
Pochettino commented: "This news merely confirms what we have known for some time – that Luke sees Southampton as the best place for him to develop.
"Luke made a tremendous impact during his first season as a professional, and he is still growing and improving with each game he plays and every training session he takes part in.
"It is very clear that he has a huge future ahead of him, and we are delighted that he shares our vision for his growth over the next few years.
"We hope that Luke's new contract will bring to an end any remaining speculation about his future, and that he can now focus fully on what promises to be an exciting season.
"He has returned for pre-season training in excellent shape, and we are expecting big things from him in the coming campaign."
In Profile – Luke Shaw
Surrey-born Luke Shaw joined Southampton at the age of eight, and went on to make rapid progress as a schoolboy.
During his teenage years, Luke split his footballing efforts between playing for the Club's Academy sides as well as for Rydens Enterprise School near Walton-on-Thames.
Shaw was a regular for Jason Dodd's Under-18 side from the age of 15 and was called up to play for England Under-16s at the prestigious Montaigu Tournament, where he scored his first international goal.
With his school, the full-back helped Rydens' Under-15 team reach the semi-finals of the English Schools' FA Cup in 2010. He also won three district cups during his time there.
At the age of 16, Shaw was named on the bench for Southampton's Carling Cup game against Preston North End at St Mary's in September 2011 and an FA Cup third-round tie at Coventry the following January.
His senior debut would arrive in the same competition later that month, when he came on as a 77th-minute substitute for Jason Puncheon in a fourth-round draw at Millwall.
Luke – along with James Ward-Prowse, Calum Chambers and Jack Stephens – was one of four youngsters drafted into the First Team ahead of the 2012/13 season, with the quartet travelling with the squad for their pre-season training camp in the French resort of Évian-les-Bains having featured in the Markus Liebherr Memorial Cup the previous weekend.
Shaw made his first senior start in August, playing the entirety of a 4-1 Capital One Cup first round win at Stevenage. He also appeared as a substitute in the third round as Saints were knocked out at Leeds United two months later.
His Premier League debut would arrive six days after that defeat at Elland Road, as he came off the bench to replace Danny Fox during the closing stages of a 2-0 loss at West Bromwich Albion.
The 17-year-old then made his first top-flight start the following weekend, putting in an impressive showing as Saints drew with Swansea City at St Mary's.
In total, he made 28 appearances for the First Team in 2012/13 as his reputation as one of the most talented young defenders in England continued to grow.
Like teammate Nathaniel Clyne, Shaw was called into the England Under-21 squad for the 2013 UEFA European U21 Championship but was forced to pull out after suffering a back injury towards the end of the 2012/13 season.
Having now committed himself to Southampton for the next five seasons, Luke will now look to continue his rapid ascent without the previous level of speculation about his future.