Women’s Prize for Fiction in its 25-year history.
Adichie, who won the prize in 2007, was chosen in a public vote from a list of all 25 winners.
Other past winners include Zadie Smith, the late Andrea Levy, Lionel Shriver, Rose Tremain and Maggie O’Farrell.
The one-off award marks the anniversary of the prize, formerly known as the Orange Prize and the Bailey’s Prize, BBC reports.
Half of a Yellow Sun is set in Nigeria during the Biafran War, exploring the end of colonialism, ethnic allegiances, class, race and female empowerment.
The book was published in 2006 and it has received global acclaim.
Adichie said; “I’m especially moved to be voted Winner of Winners because this is the prize that first brought a wide readership to my work and has also introduced me to the work of many talented writers.”
The author has received a silver edition of the prize’s annual statuette, known as the Bessie. Author and playwright Kate Mosse, the founder and director of the UK-based prize, congratulated Adichie and said she was “thrilled” Half of a Yellow Sun had won.
“Our aim has always been to promote and celebrate the classics of tomorrow today and to build a library of exceptional, diverse, outstanding international fiction written by women.
“The Reading Women campaign has been the perfect way to introduce a new generation of readers to the brilliance of all of our 25 winners and to honour the phenomenal quality and range of women’s writing from all over the world,” Mosse said.
More than 8,500 people voted and were invited to share their thoughts with the prize’s digital book club, accessing newly created online reading guides and author interviews.