Williamson, who won bronze at the 2004 Athens Games, became only the sixth British athlete to take part in six consecutive Games at London 2012 and was awarded an MBE later that year.
"I just couldn't continue to dedicate the hours needed to be competing at the top level any more," she said.
"The sport has been a part of my life since I was six years old. But I put my teaching career on hold to represent my country at events across the globe and now the time is right to just concentrate on the day job."
Archery
Olympic debutant Woodgate: nerves cost me in the heat of the Tokyo battle
01/08/2021 AT 06:58
Williamson's greatest moment was her single point victory over Shu Chi Yuan of Chinese Taipei in Athens, while she narrowly missed out on team bronze four years later in Beijing.
"All the Olympics have been special and hold some incredible memories for me," she added.
"I suppose the two that stand out would be Athens and, of course, London. And what better way to end your involvement in international competition than at the Games in your own country."
© Sportsbeat 2014
Archery
Precocious Pitman revved up for Paris after Olympic debut in Tokyo comes to an end
31/07/2021 AT 08:28
Tokyo 2020
Archery - Tokyo 2020 - Olympic Highlights
30/07/2021 AT 10:15