"As a player I have given my best, I have tried my best, I have respected the game and I have done my duty honestly and ethically to my motherland," Thirimanne posted on Facebook.
"It was a difficult decision to make, but I cannot mention here the many unexpected reasons that influenced me to take this decision willingly or unwillingly. I take this opportunity to thank the SLC members, my coaches, teammates, physios, trainers and analysts for their support and encouragement."
Thirimanne, 33, played 44 Tests, 127 ODIs and 26 T20Is after making his international debut in 2010. He was part of three T20 World Cup campaigns, including Sri Lanka's win in 2014, and played two ODI World Cups. He also led Sri Lanka in five ODIs.
"Absolute honor to have the opportunity to represent the country," he posted on Instagram. "Thanks a lot for the 13 years of amazing memories and well wishes thru out my journey (sic). See you on the other side."