The Yeoman Warder, who has not been named, will join the 35-strong guard in September after undergoing training.
She fought off competition from five other candidates, all male, and will replace a retiring Beefeater. A successful candidate must have served a minimum of 22 years in the forces as well as boast a long service and good conduct medal. The new Beefeater's scarlet livery uniform will be the same as her male colleagues' although it will be altered to fit her figure.
Her role will involve acting as a guide for tourists visiting the Tower, which is more than 900 years old.
Beefeaters have been guarding the Tower since 1485 - for 522 years. The Beefeater nickname of the Tower of London's Yeoman Warders is thought to derive from the daily ration of meat they received.
Their full title is Yeoman Warder of Her Majesty's Royal Palace and Fortress the Tower of London, and Members of the Sovereign's Body Guard of the Yeoman Guard Extraordinary.
For state occasions they wear the well-known ceremonial dress of red and gold with red stockings, a white ruff and black patent shoes.
For everyday duties they wear dark blue trimmed with red.
As the Brits don't like to make exceptions to their traditions, I think this is a milestone for female emancipation. Way to go ladies.