The 1961 novel is considered classic and has sold millions of copies
Harper Lee, author of the classic novel To Kill a Mockingbird, has died at the age of 89.
Lee had been living in a nursing home close to her childhood home in Alabama in recent years.
News of her death has been greeted with tributes across the world, including from her publisher, Random House.
Today we lost a beautiful writer. RIP Harper Lee. pic.twitter.com/aA0SgyV0j1— Random House (@randomhouse) February 19, 2016
A family statement said: "With great sadness, Ms Lee passed away in her sleep early this morning. Her passing was unexpected.
"She remained in good basic health until her passing. The family is in mourning and there will be a private funeral service in the upcoming days, as she had requested. Ms Lee was 89."
Hank Conner, Ms Lee's oldest nephew, said: "This is a sad day for our family. America and the world knew Harper Lee as one of the last century’s most beloved authors.
"We knew her as Nelle Harper Lee, a loving member of our family, a devoted friend to the many good people who touched her life, and a generous soul in our community and our state. We will miss her dearly."
The 1961 novel told the story of lawyer Atticus Finch and his fight to save the life of a black resident of Maycomb, the fictional setting of the book. It sold millions of copies around the world.
The book sold over 40 million copies and Lee won the Pulitzer Prize, but it would be her only major work published for decades.
Lee said she had little interest in writing another novel and largely disappeared from the public eye.
She suffered a stroke in 2007.
Amid controversy a prequel to To Kill a Mockingbird was released in 2015 – Go Set a Watchman.
Lee was born in 1926 in the town of Monroeville during the time of racial segregation in the United States.
Additional reporting IRN