Nobel Peace Prize laureate Johnson-Sirleaf became president in 2006, three years after the second civil war had ended, and was re-elected for a second term in 2011.
“Ellen Johnson Sirleaf took the helm of Liberia when it was completely destroyed by civil war and led a process of reconciliation that focused on building a nation and its democratic institutions,” Salim Ahmed Salim, chair of the Mo Ibrahim Foundation’s prize committee, said.
The foundation said Liberia was the only country out of 54 to improve in every category and sub-category of the foundation’s Index of African Governance since 2006.
Categories include safety and rule of law, participation and human rights, sustainable economic opportunity, and human development.
Sudanese-British businessman Ibrahim said he was “delighted” Johnson-Sirleaf had become the foundation’s first female laureate.
“In very difficult circumstances, she helped guide her nation towards a peaceful and democratic future, paving the way for her successor to follow,” he said.
Johnson-Sirleaf left office last year, and was replaced by President George Weah, a former footballer.
Winners of the Mo Ibrahim prize receive five million dollars over 10 years and 200,000 dollars annually for the rest of their lives.
Nelson Mandela became an honorary recipient of the award in 2007.
In some years the award, which was launched in 2006, has not been awarded as no candidate was considered good enough.