"I had to make the very difficult decision to finally hang up my leotard," the Briton wrote on Facebook.
"Gym has given me everything - it gave me the tools necessary to channel my ADHD throughout my childhood...and it has made me the person I am today.
"From a young age it became my dream to compete at an Olympic Games and represent Great Britain, so to have had the opportunity to do that on three separate occasions, and bring home four Olympic medals in the process, is something I will forever cherish and for which I am eternally grateful."
Louis Smith: "My Chances of being on the team now is nil"
Louis Smith: "My Chances of being on the team now is nil"The three-time Olympian explains his decision to retire from gymnastics.
A future on a different stage
Smith had intended to compete in the upcoming World Cup series with a view to qualifying for Tokyo 2020.
But he decided to retire after a change in qualification criteria and the emergence of opportunities outside of gymnastics.
He is set to star in musical theatre show Rip it Up, in London's West End this February.
No stranger to performances of this nature, Smith also won British TV dancing show Strictly Come Dancing in 2012.
Smith's Gymnastics career
Smith won two Olympic silver medals and two bronze over three Olympic Games.
His bronze at Beijing 2008 was Great Britain's first Olympic gymnastics medal since 1928.
In addition the 29-year-old clinched three World Championship silver medals, two European golds and the 2006 Commonwealth Games pommel horse title.
However Smith has also courted some controversy, having been banned for two months by British Gymnastics in 2016 for appearing to mock Islam in a video. Smith said he was "deeply sorry" for his "thoughtless actions".