Former US President Bill Clinton has honoured Muhammad Ali as a "a universal soldier for our common humanity" at the boxing legend's public memorial service in Louisville, Kentucky.
Clinton, the 42nd US President, delivered one of numerous eulogies at a public service for the boxing great Sunday morning Australian time. Comedian Billy Crystal and journalist Bryant Gumbel also spoke.
Before the service up to 100,000 people lined the streets of Louisville, Ali's home town, for a funeral procession before the burial service began.
Addressing the crowd, Clinton said the former world champ had always "written his life story".
"I think he decided before he could possibly have worked it all out, and before fate and time could work their will on him, he decided that he would not be ever disempowered," Clinton said.
"He decided that not his race nor his place nor the expectations of others, positive, negative or otherwise, would strip from him the power to write his own story."
He referred to Ali's "stunning gifts" and described him as a "truly free man of faith".
"Being a man of faith, he realised he would never be in full control of his life," Clinton said to applause.
"But being free he realised that life still was open to choices. It is the choices that Muhammad Ali made that have brought us all here today in honour and love."
WATCH: Bill Clinton remembers Muhammad Ali: 'honor him by letting our gifts go among the world' https://t.co/VkdJwRwwUk— ABC News Politics (@ABCPolitics) June 10, 2016
He said Ali's life post boxing was the most important because he never let Parkinson's disease get the better of him.
The former president said his enduring memory of Ali was in three parts.
"The boxer I thrilled to as a boy, the man I watched take the last steps to light the Olympic flame when I was President ... and the children whose lives he touched, the young people he inspired."
Clinton said Ali's impact on others was his most important gift of all.
"It's the gift we all have that should be most honoured today. Because he released them to the world. "
Earlier at the service, Ali's widow Lonnie said Muhammad's life provided useful guidance for today's America.
"Muhammad was not one to give up on the power of understanding, the boundless possibilities of love, and the strength of our diversity," she said.
"He counted among his friends people of all political persuasions, saw truth in all faith and the nobility of all races."
The funeral procession through Louisville reportedly stretched over 40 kilometres and was followed by a private burial service for the former world champion at Louisville's Cave Hill Cemetery.