Sasha was put to sleep yesterday morning after keepers at the park noticed “odd changes” in her behaviour.
The animal was also said to be unable to compete with her three-year-old daughters, Natalia and Dominika.
Highland Wildlife Park’s Facebook page stated: “Originally thought to be due to old age, as Amur tigers in the wild seldom make it past 12-years-old, it became clear over recent weeks that her health and wellbeing was starting to deteriorate.
“Sadly, the continuing changes in the social hierarchy of our Amur tiger group and other recent observations strongly indicated probable health or senility issues with Sasha.
“After consultation with her keepers and the vets responsible for her care, it was decided the most appropriate course of action was to put her to sleep.”
Sasha arrived at the park, in Kingussie, near Aviemore, along with her long-term mate Yuri from Edinburgh Zoo on September 25 2008.
She lived with Natalia and Dominika after Yuri was put down in 2010, aged 17.
It is understood there are only around 500 Amur tigers, previously known as Siberian tigers, still living in the wild.
Together, Yuri and Sasha produced a total of nine cubs.
A post-mortem examination will be carried out, which the park hopes will explain the changes in Sasha’s behaviour, as well as providing information which could further the understanding of health issues suffered by older tigers.