The World Bank veteran, 70, is a trailblazer. She was Nigeria's first woman finance minister and is the first woman and the first African to run the WTO.
With her no-nonsense style and disdain for red tape, she positioned herself as someone who could bang heads together and get business done.
Okonjo-Iweala has pulled off some breakthroughs at the global trade body, notably sealing a long-stalled deal on curbing subsidies for harmful fishing practices.
But now she must steer the WTO through the US presidency of Donald Trump -- who paralysed the organisation in his first term and opposed her initial candidacy for the leadership.
'Forget business as usual'
In March 2021, Okonjo-Iweala took over an organisation mired in multiple crises and struggling to help member states navigate the severe global economic slump triggered by the coronavirus pandemic.
"Forget business as usual," she pledged before taking the reins.
Since taking over the 166-member WTO, Okonjo-Iweala has overseen two of its biennial ministerial conferences.
The 2022 gathering at the WTO's Geneva headquarters saw the director-general secure results and demonstrate the round-the-clock stamina essential to striking international trade deals.
Countries agreed the first stage of a long-elusive deal on curbing harmful fishing subsidies, and struck agreements on bolstering food insecurity and temporarily waiving patents on Covid-19 vaccines.
The second conference, in Abu Dhabi this year, secured nothing more than a temporary extension of an e-commerce moratorium, casting fresh doubt on the WTO's effectiveness.
While Okonjo-Iweala criss-crosses the world from conferences to meetings of top finance ministers and heads of diplomacy to try to move things forward, she rarely holds press conferences.
She was the sole candidate to lead the WTO for four years from September 2025.
"Ngozi brings a huge amount of personal authority, credibility and capability to what's a challenging and difficult role," Britain's trade minister Douglas Alexander told AFP last month.
"She clearly has an ambitious agenda in relation to that interaction of trade and environment."
He praised her "steady leadership, her deep commitment to the interests of the Global South, and her understanding, as a former finance minister, of the imperative of trade for all of our economies".
Harvard, MIT training
Born in 1954 in Ogwashi Ukwu, in Delta State, western Nigeria, Okonjo-Iweala is the daughter of a traditional ruler.
She and her neurosurgeon husband, Ikemba Iweala, have four children and five grandchildren.
She is often surrounded by her loved ones and she always warmly thanks her husband, who attended both ministerial conferences, for his support.
A development economist by training, she spent much of her life in the United States, graduating from Harvard -- where she later sent her four children -- before earning a master's degree and a doctorate from the Massachusetts Institute of Technology.
Okonjo-Iweala had a 25-year career at the World Bank, eventually becoming its number two.
She was the Washington-based institution's managing director and ran for the top job in 2012.
Her first term as Nigeria's finance minister, from 2003 to 2006, was followed by two months as the foreign minister.
She was the first woman to hold both positions.
She returned to the finance minister brief from 2011 to 2015 under president Goodluck Jonathan.
Okonjo-Iweala portrayed herself as a champion against Nigeria's rampant corruption -- and said her own mother was even kidnapped over her attempts to tackle the scourge.
But her critics charged she did not do enough to stop corruption while in power.
Okonjo-Iweala also held a slew of directorships at places like Standard Chartered Bank and the Rockefeller Foundation.
She was on the Twitter board of directors and chaired Gavi, the Vaccine Alliance.
When Roberto Azevedo stepped down early as WTO head in August 2020, Okonjo-Iweala put herself forward and saw off seven other candidates.
