Conversations about gender equality "can't happen without men", the Duchess of Sussex has said at a roundtable discussion on the issue.
Meghan was joined by the Duke of Sussex, and jokingly thanked delegates for "letting him crash the party".
Harry was described as a "surprise appearance" by co-organisers, the Queen's Commonwealth Trust.
Young ambassadors from around the world took part in the talks, which were held at Windsor Castle.
The couple arrived together in an electric Audi - driven by the duke - after they were accused of hypocrisy for using private jets while supporting environmental campaigns.
The participants - who represented organisations from countries including South Africa, Nigeria, Iraq, Malawi and Bangladesh - shared their personal achievements and the best practices that had helped them overcome complex challenges.
Beginning the discussion, Meghan, seated next to her husband, told the group: "In terms of gender equality, which is something I have championed for a long time, I think that conversation can't happen without men being a part of it.
"So for this reason it made complete sense to let him [Harry] join today. So thank you for letting him crash the party."
Among those to share their experiences with the royal couple was the founder of the South African organisation Motholung Network Against Women and Child Abuse, Lebogang Bogopane.
"I got married very young and experienced domestic violence," she said. "My mother is a survivor and I'm also a survivor. One day I said 'I'm tired, this needs to stop.'"
The roundtable was led by Queen's Commonwealth Trust chief executive Nicola Brentnall and moderated by One Young World counsellors, social media influencer Rossana Bee and Canada's first openly gay Olympic gold medallist, Mark Tewksbury.
Mr Tewksbury said the duke's appearance at the event was a "wonderful surprise".
"I guess we should have known because there were two empty chairs there, but I just assumed that an assistant was going to come along," he said.
The founder of the first Iraqi LGBT+ organisation, Amir Ashour, who also took part in the roundtable, said the duke's attendance was an indication of how important the issue was to the royal couple.
"They were asking questions and getting engaged," the 29-year-old said, adding that he was "surprised at how genuine they were".
Harry and Meghan are president and vice president of the Queen's Commonwealth Trust respectively.
And Meghan is a long-standing supporter of One Young World, which she called "the best think tank imaginable".
The One Young World Summit is a four-day global forum for young leaders, which aims to bring together 2,000 young people from more than 190 countries to accelerate social impact.
On Tuesday, Meghan attended the summit's opening ceremony at the Royal Albert Hall in London.
She has previously spoken about her belief that men can also be feminists - and, while pregnant, said she wanted her baby to be a feminist, whether they were a girl or a boy.
The roundtable on Friday was the couple's first public engagement since an emotional ITV documentary, when they described the pressure they had faced from intense media scrutiny.