Hamilton, who has 63 test caps, and appeared at two previous World Cups, used his twitter account to make his decision public.
"Today is both a sad day and a day that I feel extremely proud to have had," he tweeted.
"Never in a million Saturday afternoons did I think I would have represented this beautiful country of Scotland 63 times on the rugby field.
"I have loved every single moment of wearing the thistle and feel extremely humble to have done it for nine years."
The 6 foot 8 inch Hamilton was born in England and appeared for them at under-21 level but opted for Scotland at senior level, making his debut in 2006.
In the 2013-14 season he moved from Gloucester Rugby to France to play for Montpellier, returning to join Saracens the following season.
(Reporting by Steve Tongue; editing by Sudipto Ganguly)
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