Richardson was appointed Scotland team manager in May 2004 and has overseen all their fixtures in RBS 6 Nations, autumn internationals, overseas tours and the Rugby World Cup ever since.
In addition to his role with the Scotland team, Richardson was Scottish Rugby's head of rugby operations, effectively overseeing administrative and management support for all Scottish Rugby's representative teams, including Magners League outfits Glasgow Warriors and Edinburgh.
Previously in the Army, Richardson served with the Royal Scots for 20 years, reaching the rank of Major and taking part in operational tours in Northern Ireland, the first Gulf War, Sierra Leone, Afghanistan and Bosnia.
"It's been a great privilege for me to be involved with the Scotland team for the last six years and I have many happy memories of the extraordinary commitment and professionalism I have seen from players, management and Murrayfield staff alike over that period," said Richardson, who has worked under three Scotland head coaches in Matt Williams, Frank Hadden and Andy Robinson.
Richardson was named logistics manager for the 2009 Lions tour to South Africa and is held in extremely high regard within the game.
His decision to look for a new challenge elsewhere leaves the Scottish Rugby Union looking for a new team manager, although current head coach Robinson insists they will not be rushing the process.
Scotland's next fixture isn't until the autumn campaign, with the SRU expected to name Richardson's successor prior to the clash against New Zealand on the weekend of November 13/14.
"The work that Guy and his team have put into Scottish Rugby over the last few years has been hugely appreciated by the players," said Robinson.
"We wish him well in his new role and we will be considering the recruitment process for his successor over the next few weeks."
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