The sailor from Lower Saxony fell during a stop in the Brazilian port of Salvador de Bahia, crashing from the vessel's rigging onto the deck and dying of her injuries in a nearby hospital, the navy said.
The young woman's family in the county of Holzminden has been notified. She had been in the German military for three and a half years and belonged to the Mürwik naval academy in Flensburg.
The accident occurred during a climbing exercise, but exact circumstances remain unclear and the investigation has not been concluded, the navy said.
The three-mast barque set sail from Kiel on August 20 with 229 sailors on board for a training mission in South America set to be the longest in the ship's history. It is expected home in June 2011.
The death was the sixth on board the ship since it was built in 1958, a Navy spokesperson said.
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The last deadly accident on the ship occurred in September 2008, when another female officer candidate, 18, fell overboard during her night watch on the North Sea.