"Her Serene Highness Princess Marie von und zu Liechtenstein died on 21 August 2021 at 4:43 pm [14:43 GMT] in the hospital in Grabs", Saturday's statement says.
According to the release, the Princess passed away "peacefully" in the presence of her family.
She had been hospitalised after suffering a stroke on 18 August and her health "steadily deteriorated" after that, the Princely House of Liechtenstein said.
Marie was born in Prague on 14 April 1940 and married Hans-Adam II in 1967 in Liechtenstein's capital, Vaduz. The Princess and Prince of Liechtenstein have a total of four children together.