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The sprint freestyle specialist made her Olympic debut at Beijing 2008 and narrowly missed out on medals at both London 2012 and Rio 2016.
She finished just 0.02 seconds off the podium in the 50m freestyle in Rio.
"Stepping away from the pool is quite a scary decision," said Halsall, 26.
Halsall won three gold and seven silver medals at the Commonwealth Games, having made her international debut at Melbourne in 2006.
She was part of the gold medal-winning 4x100m medley relay team at the 2015 World Championships, and also won gold in the 50m backstroke at the 2016 European Aquatics Championships.
Halsall's retirement statement in full:
Announcing my retirement from swimming is a weird concept to me as I've never seen it as a career or a job. Just as a hobby that I've loved doing and happened to be OK at.
However I've done it for over a decade and there are so many people who have committed time, money, wisdom and knowledge into my journey that I will forever be thankful for. Stepping away from the pool is quite a scary decision for someone who's whole adult life to date has revolved around swim, weights, diet, peeing in a pot whilst someone watched, outdoor swim camps (yey) and lots of napping.
I am very much looking forward to the next chapter of my life and the normality of eating and drinking what I want, the only time someone watches me pee is when I leave the door open by accident and the dog comes in, and experiencing the mythical bank holidays. I will miss my daily naps and choosing to do sets of backstroke while training outdoors just to get an even tan. It's time to close this chapter of my life and move on to the next.
Swimming has taught me so much and given me opportunities that no other career could. So for me this is just a thank you note to everyone who has supported me for being part of a fantastic set of memories.

Marco Archer Cardoso Moreira, 53, was arrested in 2003 after police at Jakarta airport found  13.4 kg of cocaine hidden in his hang glider.
Brazil says he was the first Brazilian national to be executed abroad and has warned it will damage relations.
Five other convicts from Indonesia, Malawi, Nigeria, Vietnam and the Netherlands, were executed on Sunday.
Convicted of drugs charges, they faced a firing squad in Central Java province shortly after midnight local time.
Five were executed on the island of Nusa Kambangan and the other one, a Vietnamese woman, was executed in the small central Javanese town of Boyolali.
Brazilian President Dilma Rousseff said in a statement that she was "outraged and dismayed".
"Relations between the two countries have been affected," said Ms Rousseff.
"The Brazilian ambassador to Jakarta has been recalled for consultations," she added.
The Netherlands has also recalled its ambassador, after Foreign Minister Bert Koenders called the execution of Dutch citizen Ang Kiem Soe, 52, "an unacceptable denial of human dignity and integrity".
Indonesia has some of the world's toughest drug laws. The country resumed executions in 2013 after an unofficial four-year moratorium.
The country's Attorney General Muhammad Prasetyo said "hopefully, this will have a deterrent effect".
President Joko Widodo has said that he will show no mercy towards drug criminals because they have ruined the lives of so many.
Ms Rousseff had made a plea for clemency on Friday, but it was rejected by Mr Widodo.
She told her Indonesian counterpart that she respected the sovereignty and judicial system of his country but as a mother and head of state she was making the appeal for humanitarian reasons.
Brazil says Mr Widodo said he understood the Brazilian president's concern but said he could not commute the sentence as the full legal process had been followed.
Human rights group Amnesty International urged the Indonesian government to halt executions immediately, and eventually abolish the death penalty.
Moreira said in a video recorded by a friend that he regretted trying to smuggle cocaine into Indonesia.
"I am aware that I committed a serious offence, but I believe I deserve another chance. Everyone makes mistakes."
A second Brazilian national, Rodrigo Muxfeldt Gularte, remains on death row in Indonesia, also convicted with drug trafficking offences.
Brazil abolished the death penalty in times of peace when it became a republic in 1889.
Britain's three-time Olympian Fran Halsall, who won more than 30 medals at world, European and Commonwealth level, has announced her retirement after a 10-year international career.
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Brazil says it is "outraged" by the execution of one of its citizens in Indonesia for drug trafficking.