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Fortune praised Ardern for her leadership after the Christchurch mosque attacks.
"Jacinda Ardern had already broken new ground as a pregnant woman — and then a new mother — leading a nation," they wrote in their list of the Top 50 World's Greatest Leaders.
"And this year, the 38-year-old Prime Minister showed the world her fullness as a leader as she deftly, empathetically, and humbly navigated New Zealand through the worst terror attack in its history, after 50 were killed at two mosques in Christchurch in March."
"Rallying people behind the theme 'We are one', she channelled the country's — and Muslim community's — grief as she opened speeches with Arabic greetings and quietly wore a head scarf."
Fortune also said she set a standard for dignity by refusing to say the attacker's name and won support for a ban on semi-automatic weapons.
"Future leaders can look to Ardern for a master class in how to guide a country through a crisis," the magazine wrote.
Her second place ranking saw her leap up from 29th place on the same list year.
Fortune put Bill and Melinda Gates on the top of their list for the work their foundation has done in fighting global health crises.
US special counsel Robert Mueller was listed in third place. His report into possible Russian interference in the 2016 United States elections was released today.
This week, Time Magazine featured Ardern in its list of the world's 100 most influential people of 2019.
It is the second year running the PM has been on the Time list.
London mayor Sadiq Khan, writing for Time, said: "Jacinda Ardern's leadership since the attack has been an inspiration to us all."
"Not only is she delivering swift action on gun control, she has sent a powerful message around the world about our shared values — that those who seek to divide us will never succeed, and that New Zealand will always protect and celebrate the diversity and openness that make our countries so great."
Kahn went on to state that Londoners stood "shoulder to shoulder with the people of Christchurch".
"We will never forget that when terror sent ripples of fear through communities around the world, New Zealand's Prime Minister proudly stood up for hope, unity and inclusiveness in the face of fear, division and hatred."