–is executed (at age 24) by order of a Death Warrant signed by her cousin Elizabeth I.
The two had never met.
Mary had been crowned at age of 9 months in December 1542. Her father, James V of Scotland had died when she was 6 days old. She spent the last 19 of her 24 years of life in custody in England.
Elizabeth I would, after the execution of her cousin, later assert (and historians would agree) that although she had signed the Death Warrant, she had never given the actual green light for the execution. Her Privy Councillor, William Davidson was then, as a consequence, imprisoned in the Tower of London.
Note: Mary I of England (“Bloody Mary”) had died at age 42 back in November, 1558.