Rosa Parks, the black woman whose 1955 protest action in Alabama marked the start of the modern US civil rights movement, has died at the age of 92.
Mrs Parks' refusal to give up her seat to a white man on a bus prompted a mass black boycott of buses, organised by Baptist minister Martin Luther King Jr.
His protest movement brought about the 1964 Civil Rights Act, which outlawed racial discrimination in the US.
Mrs Parks' lawyer said she died in her sleep at her home in Detroit, Michigan.
It was revealed last year that she was suffering from progressive dementia.
"She sat down in order that we all might stand up - and the walls of segregation came down," civil rights leader Jesse Jackson said.
He said her legacy would never die, and added: "In many ways, history is marked as before, and after, Rosa Parks."
"The nation lost a courageous woman and a true American hero," Massachusetts Democrat Senator Ted Kennedy said.
"Her quiet fight for equality sounded the bells of freedom for millions," he said.
Detroit Mayor Kwame Kilpatrick said: "She's an example for all people. For one, I would not be standing here but for her sitting down and standing up at the same time."
'I had a right'
Mrs Parks was a 42-year-old seamstress when she made history.
On 1 December 1955, Mrs Parks refused to give up her seat on a bus in Alabama to a white man, defying the law. She was arrested and fined $14.
For years before her arrest, Mrs Parks had been active with local civil rights groups, which were looking for a test case to fight the city's segregation laws.
Her arrest triggered a 381-day boycott of the bus system organised by the then little-known Rev Luther King Jr, and the protest led to the desegregation of the transport system.
Speaking in 1992, Mrs Parks said of her famous bus protest: "The real reason of my not standing up was I felt that I had a right to be treated as any other passenger. We had endured that kind of treatment for too long."
She was awarded the Presidential Medal of Freedom in 1996, and the Congressional Gold Medal, the nation's highest civilian honour, three years later.
Democratic Congressman John Conyers, from whom she worked in Detroit from 1965 until she retired in 1988, described her as "an almost saint-like person".
"She was very humble, she was soft-spoken, but inside she had a determination that was quite fierce."