Madeleine Albright, a Czech immigrant who went on to become the first female secretary of state in US history, has died aged 84.
A long-time foreign policy veteran, Albright became America's top diplomat in 1997 during the Clinton government.
Often hailed as "a champion of democracy", Albright was instrumental in efforts to end ethnic cleansing in Kosovo.
Her death from cancer was confirmed by her family in a statement.
"She was surrounded by family and friends," the statement said. "We lost a loving mother, grandmother, sister, aunt and friend."
Among those to pay tribute to her after the announcement of her death were former President Bill Clinton and Hillary Clinton, who later followed in her footsteps as Secretary of State.
"Few leaders have been so perfectly suited for the times in which they served," the Clintons said. "Because she knew first-hand that America's policy decisions had the power to make a difference in people's lives around the world, she saw her jobs as both an obligation and an opportunity."
Nato's current Secretary General, Jens Stoltenberg, said after the announcement that Albright "was a force for freedom" and an "outspoken champion of Nato".
Former US President George W Bush said that Albright "understood first-hand the importance of free societies for peace in our world".
UK Foreign Secretary Liz Truss tweeted that the world "needs to stand by" Albright's values "more than ever".