The Australia and Queensland captain dropped the bombshell news at a Melbourne press conference on Tuesday, just three weeks out from the State of Origin series.

The physical and mental toll of Origin, as well as a desire to spend more time with his family were behind his decision, while Smith said he hoped it would extend his NRL career with the Storm.

Flanked by Walters and with his wife Barbara and three kids watching on, the 34-year-old said now was the right time to finish up a career that encompassed a record 42 Origin appearances - including 11 series wins - and 56 Tests including two World Cup triumphs.

"The decision is a combination of the impact that representative football had on me and my family," Smith said.

"It's a decision that I did take a lot of time to come to but in the end the reasons for not playing on far outweighed reasons to play on this year.

"I feel really good. I feel happy. When I spoke to Kev about the decision it was almost as though a weight was off my shoulders."

Smith said he'd started thinking about it last year, when he was unable to back up and play for the Storm the weekend after each Origin game as he'd done in the past.

"Last year, more than any other year, the Origin series in particular had an effect on me both physically and mentally," said Smith.

"Looking back on it now I just don't think that's fair for myself, I don't think that's fair on my family and also my teammates back here at Melbourne Storm.

"I couldn't back up after any of those Origin matches and maybe that was a sign there that it was time, because I have always been very proud of my ability to back up and it's something I've looked forward to."

Smith said those weekends, when unable to play for Melbourne, he was lying on the couch or in bed exhausted, and he believed few realised the drain of playing at that level.

His absence from his family through the Origin period and then six weeks away on World Cup duty with the Kangaroos also contributed to the decision.

"There's a few important things happening now with my family with school and with their junior sport that I miss out on," Smith said.

"That's a big sacrifice but it's a bigger sacrifice for them."

Maroons coach Kevin Walters said he had an inkling that Smith was wavering about Origin in their discussions through the year.

"I just didn't get the same vibe that I've had over the last couple of years with him, with his enthusiasm and drive," Walters said.

"We've lost our captain, our leader and our goal-kicker so it's a big loss for Queensland but it had to happen one day."

Smith's exit follows the representative retirements of fellow Australian and Queensland greats Johnathan Thurston and Cooper Cronk announced last year, leaving a huge void for Walters to fill.

But Smith said he didn't let the absence of his longtime teammates influence his call on his own future.

"At no time did any other person's retirement or what the make up of the team this year come into my calculations," he said.

"I still believe Queensland can win this year."

Making his debut for Queensland in 2003, Smith has captained the side since 2012.

In his Origin career he missed just one game - the series opener in 2010 due to injury - and won a record 26 matches.

Smith's exit is likely to springboard Brisbane hooker Andrew McCullough into a Queensland Origin debut in the June 6 series opener at the MCG, while Jake Granville of the Cowboys could be another option.

Darius Boyd, Billy Slater or Bowraville’s Greg Inglis are the most likely candidates to take over the captaincy, however Boyd has battled form and fitness at Brisbane this season.

Australian Associated Press