Adlington, who currently holds the world record in the 800 metres freestyle, won two golds in Beijing in 2008 and two bronze medals at London 2012.
"I love swimming but as a competitive element and elite athlete I won't compete any more," she told reporters.
"I have achieved everything I wanted to. Some people want to milk it all they can. I've always said I wanted to finish on a high, despite my love of the sport.
"I did feel old at 23, female distance swimming is going a lot younger as was evident in London.
"I can't compete with that and can't do the same level of work. I need a lot more rest and recovery. I think it was the perfect time."
Adlington had already announced she would not compete at the Rio 2016 Olympics in September and said her work outside of elite competition was now her main focus.
"I'm very proud of what I have achieved so far, but my journey is not finished yet," she said on her personal website.
"My vision is that every child in Britain will be able to swim 25 metres by the time they leave primary school. Being able to swim is such a wonderful life skill, and I see this as my greatest challenge in swimming."
Adlington, who finished third behind 15-year-old American Katie Ledecky in the 800 metres freestyle at the London Games, also won World, European and Commonwealth Games gold medals.
The 18-times Olympic gold medal winner Michael Phelps led the tributes.
"Our paths have crossed many times over the years - at meets and through a shared sponsor," he said.
"Her accomplishments speak for themselves, she has been a great representative for British Swimming and the sport overall. I congratulate her on a fantastic career and wish her all the best in the future."
Her retirement comes a day after British Swimming announced a new leadership team with Adlington's coach Bill Furniss taking up the head coach's role at the national federation.