Mrs King, the widow of civil rights icon Martin Luther King Junior, was remembered with lively and soulful hymns and prayers as she lay in a closed casket covered in flowers at the New Birth Missionary Baptist Church outside Atlanta.
US President George W Bush paid tribute to Mrs King, recalling her determination to keep her husband's non-violent quest for equality alive after his 1968 assassination.
He described her as "one of the most admired Americans of our time".
"Americans knew her husband only as a young man," he said, offering the sympathy of all Americans to the King family.
"We knew Mrs King in all the seasons of her life, and there was grace and beauty in every season."
Mr Bush ordered federal facilities to fly flags at half-mast on Tuesday in her honour.
Her funeral took place at the New Birth Missionary Baptist Church, which seats 10,000 people, in Lithonia, east of Atlanta, where her daughter Bernice is a minister.
An estimated 150,000 people have paid their respects to Mrs King in recent days, filing past her open casket in the state Capitol building.
Mrs King, who died last week aged 78, is the first woman and the first African-American to lie in honour in Georgia state Capitol.
Former US presidents Jimmy Carter, Bill Clinton and George Bush attended the funeral along with their wives.
Since Mrs King's death on January 30, she has been remembered for keeping her husband's message alive after he was assassinated on April 4, 1968 in Tennessee.
Four days after his death, Mrs King led 50,000 people in an equal rights march through the streets of Memphis.
Speakers recalled her strength in taking over her husband's battle as a widowed mother of four, despite threats of violence.
"She became not only a national presence, but an international icon, opposing apartheid in South Africa in the 1980s with the same fervour that she had challenged prejudice in America in the 1960s," Senator Ted Kennedy said.
Former president Clinton told reporters he had memories about Mrs King from the period after her husband’s death as well as during his time in office.
Mrs King was born in racially segregated Alabama and met her husband in Boston when she was a music student and he was studying for a doctorate in theology.
In 1969 she founded the Martin Luther King Jnr Centre for Non-violent Social Change in Atlanta, and in 1986 saw her husband's birthday established as a national holiday.