The announcement was made a few hours before the duchess takes part in a discussion panel, organised by the Trust, of leading feminists and national figures to mark International Women’s Day.
Nicola Brentnall, the Trust’s chief executive, said: “We are particularly delighted that the first opportunity of formally working together with Her Royal Highness comes on International Women’s Day.
“This squares perfectly with our focus on amplifying the work and contribution of those furthest away from power.
“Women across the Commonwealth and the globe often face the biggest impediments to success.
“So we are delighted to have our vice-president’s support in helping others to overcome those obstacles.”
Last year the Duke of Sussex said Meghan was “hugely excited” to be joining him in his work as Commonwealth youth ambassador, a post bestowed by the institution’s head, the Queen.
The trust works to champion, fund and connect young leaders around the world who are driving positive social change, serving their communities and providing hope, work and self employment opportunities for others.
Lord Geidt, the Trust’s chairman and the Queen’s former private secretary, said: “The support and encouragement which Her Royal Highness will bring to the young leaders with whom we work promises to have a profound effect.”
During the discussion Meghan will appear alongside singer Annie Lennox, former prime minister of Australia Julia Gillard and others to debate a range of issues affecting women today.
The group will also chat about the positive opportunities that come when women are given wider access and equal opportunities.
The duchess has made women’s empowerment a key part of her campaigning work and during her recent tour of Morocco with the duke told a group of female executives and entrepreneurs: “Women have to challenge everywhere in the world.”
Lennox is founder of The Circle, an organisation supporting and empowering women’s lives around the world, while Ms Gillard is chairwoman of the Global Institute for Women’s Leadership at King’s College London, which is hosting the event.
Other members of the panel include Adwoa Aboah, who set up the open social discussion platform Gurls Talk, Chrisann Jarrett, founder of the equal access to higher education campaign Let Us Learn, and Angeline Murimirwa, executive director of the Campaign for Female Education in Africa and co-founder of Cama, a pan-African network of young female leaders.
The panel will be chaired by Anne McElvoy, senior editor of The Economist and columnist with the Evening Standard.