Population Matters said it was recognising Harry and Meghan with the “Special Award” for reducing their impact on the environment by not having any more children following the birth of their daughter this year.
The Sussexes, who quit as senior working royals last year, had baby Lilibet “Lili” Diana on June 4, following the birth of their son Archie Mountbatten-Windsor on May 6, 2019.
The UK-based charity Population Matters, which campaigns to achieve a sustainable population, said the couple were being recognised as “a role model for other families”.
A spokesman said: “In choosing and publicly declaring their intention to limit their family to two, the Duke and Duchess of Sussex are helping to ensure a better future for their children and providing a role model for other families.
“Having a smaller family reduces our impact on the Earth, and provides a better chance for all our children, their children and future generations to flourish on a healthy planet.
“We commend the Duke and Duchess for taking this enlightened decision, and for affirming that a smaller family is also a happy family.”
Harry mentioned his intention to have no more than two children during a talk with chimpanzee expert Dr Jane Goodall in Vogue magazine in 2019.
During the interview, he said the Earth is “borrowed”, adding:
“Surely, being as intelligent as we all are, or as evolved as we all are supposed to be, we should be able to leave something better behind for the next generation.”
Harry and Meghan have been given the award with nine others, to mark the UN’s World Population Day on Saturday.
Each recipient will receive a £500 donation for a charity of their choice.
Other winners include Wendo Aszed, founder of a women’s empowerment and community health project in rural Kenya, Emma Gannon, author of Olive, a best-selling novel addressing the choice to be childfree, and Nairashe Maritsa, a teenager fighting child marriage in Zimbabwe.