Prime Minister said her "thoughts are with" King Charles III following the death of Queen Elizabeth II.
Ms Truss wrote on Twitter: "On behalf of a grieving nation I offer my deepest condolences on the passing of Her Majesty.
"She was the rock on which modern Britain was built.
"The thoughts of this government and this nation are with His Majesty The King and his family."
Buckingham Palace confirmed on Thursday that Queen Elizabeth II had died peacefully at Balmoral.
The statement read: “The Queen died peacefully at Balmoral this afternoon.
"The King and The Queen Consort will remain at Balmoral this evening and will return to London tomorrow.”
Speaking following the news, Ms Truss said outside No.10: “We are all devastated by the news that we have just heard from Balmoral, the death of Her Majesty The Queen is a huge shock to the nation and to the world.
“Queen Elizabeth II was the rock on which modern Britain was built."
She added: “It’s an extraordinary achievement to have presided with such dignity and grace for 70 years. Her life of service stretched beyond most of our living memories.
“In return she was loved and admired by the people in the United Kingdom and all around the world.
“She has been a personal inspiration to me and to many Britons – her devotion to duty is an example to us all.”
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Liz Truss No.10
Queen Elizabeth II died on Thursday aged 96 Kirsty O'Connor