Michael R. Bloomberg, the billionaire and former New York City mayor, is giving $600 million to the country’s four historically Black medical schools, which account for a significant percentage of all medical degrees awarded to Black doctors.

Through his charitable organization, Bloomberg Philanthropies, Mr. Bloomberg is giving $175 million each to Meharry Medical College in Nashville, Morehouse School of Medicine in Atlanta and Howard University College of Medicine in Washington. These donations are believed to be the largest ever to any single H.B.C.U., surpassing the $100 million gift that Spelman College in Atlanta announced in January.

The foundation is also giving $75 million to Charles R. Drew University of Medicine and Science in Los Angeles and an additional $5 million to help start a new medical school at Xavier University of Louisiana in New Orleans.

Dr. James E.K. Hildreth, president and chief executive of Meharry Medical College, said in an interview that the gift was “just a major, major investment that will have generational impact.”

The money is targeted at the medical schools’ endowments, which an announcement on Tuesday morning described as “significantly underfunded” as a result of entrenched discrimination and lagging federal and state support.

Despite their small number, the historically Black medical schools are strong engines of social mobility for their graduates, and contributors to the well-being of Black communities, research shows.