"We are deeply troubled that the budget proposal disproportionately affects the poorest people, abroad and at home," Sue Desmond-Hellmann, CEO of the Foundation, said in a statement to the press.
Trump's budget heavily favors defense and aid for veteran affairs, and it slashes funding for a number of departments, including energy, transportation, education, agriculture, and the environment.
In the statement, Desmond-Hellmann pointed to the leaps public health organizations have made in reducing cases of infectious disease and lifting people out of poverty.
Over the last 25 years, vaccines and other interventions have prevented some 122 million child deaths.
"Foreign aid, and investments in research and development, have played a vital role in achieving this progress," she said. "Empowering people to lead healthy, productive lives creates more stable societies, which are critical to our national security."
When governments cut funding for departments that oversee public-good organizations, such as energy and the environment, underserved communities often bear the greatest burden. Basic necessities - like clean water for drinking and bathing - may never reach them.
"In the United States, we must continue to focus on expanding access to education and economic opportunity," Desmond-Hellmann said. "The proposed cuts will ultimately make America, and the world, less prosperous and less safe."