Melinda French Gates will step down as co-chair of the Bill & Melinda Gates Foundation, the non-profit she and her ex-husband Bill Gates founded and built into one of the world’s largest philanthropic organisations over the past 20 years.

“This is not a decision I came to lightly,” French Gates posted on the X platform on Monday.

“I am immensely proud of the foundation that Bill and I built together and of the extraordinary work it is doing to address inequities around the world.”

She praised the foundation’s CEO, Mark Suzman, and the foundation’s board of trustees, which was significantly expanded after the couple announced their divorce in May 2021.

“The time is right for me to move forward into the next chapter of my philanthropy,” Ms French Gates wrote in her statement.

She organises some of her investments and philanthropic gifts through her organisation, Pivotal Ventures, which is not a non-profit.

Bill Gates thanked Ms French Gates for her “critical” contributions to the foundations in a statement, saying, “I am sorry to see her leave, but I am sure she will have a huge impact in her future philanthropic work.”

Ms French Gates will receive 12.5 billion dollars as part of her agreement with Mr Gates, which she said would commit to future work focused on women and families.

The Gates Foundation did not immediately return a request for comment about whether those assets would come from the foundation itself. In an emailed statement, the foundation said that Mr Suzman announced the decision to employees on Monday.

“After a difficult few years watching women’s rights rolled back in the US and around the world, she wants to use this next chapter to focus specifically on altering that trajectory,” Mr Suzman said of Ms French Gates.

Mr Suzman said he knew many had joined the foundation in part because of their admiration for her advocacy, especially around gender equity.

“I know how beloved Melinda is here,” Ms Suzman wrote.

The Gates Foundation holds 75.2 billion dollars in its endowment as of December 2023, and announced in January, it planned to spend 8.6 billion dollars through the course of its work in 2024.