When Pattie Sellers helped start Fortune’s list of the world’s most powerful women more than two decades ago, it served as a showcase of women at the top of their fields. Now, Ms. Sellers and Nina Easton, who helped expand the franchise, are starting an initiative to ensure that there are more women who rise.

On Tuesday, Ms. Sellers and Ms. Easton announced Journey, a nonprofit group aimed at addressing the “pyramid effect,” in which the share of women shrinks as they rise up the corporate ranks.

The new group connects 25 fellows with 25 mentors, who include some of the country’s most influential executives, such as Mary Barra of General Motors, Mellody Hobson of Ariel Investments and Dina Powell McCormick of Goldman Sachs.

“These women, because of who they are and their own journeys to the top, they know how to address the problem because they’ve lived it,” Ms. Sellers said.

For the fellows, Journey is seeking women across the private sector, with a focus on minorities or those facing challenges, socioeconomic or otherwise.

“We’re looking to help them get beyond the barriers,” said Beverly Kirk, Journey’s executive director. The group hopes that fellows will develop long-lasting relationships with a variety of mentors who will help guide their careers.

“It’s about building bonds,” Ms. Easton said.

Women hold fewer than 10 percent of Fortune 500 chief executive spots. The pandemic has driven millions of women from the work force, in part the result of a child care crisis. The numbers are even worse for Black women. Journey’s intentionally small fellowship class is intended in part to allow for open dialogue about the personal and professional challenges behind those numbers.

“We began to think about how these conversations need to be much more intimate, so that we could drill down and have very candid conversations,” said Rosalind Brewer, the chief executive of Walgreens Boots Alliance.

Relationships developed through the program are intended to open doors that have otherwise remained mostly shut for women. Companies founded by women in the United States raised only 2 percent of total venture funding last year, according to PitchBook.

“Until there is more diversity at the top, you’re going to have less money going to female founders and certainly to diverse female founders,” said Susan Lyne, a co-founder of BBG Ventures.

“For people to give you an opportunity where they have to take some risk,” said Amy Chang, who sits on the boards of the Walt Disney Company and Procter & Gamble, “they need to have heard about what you can do, and they need to trust that they should take this risk on you.”

Ultimately, Journey’s success will be measured by that of its fellows. “That’s really what I think will be the judge of if it’s successful,” said Ginni Rometty, a former chief executive of IBM. “If we can accelerate their timelines to be in real positions of influence.”