New York Mayor Michael R. Bloomberg has pledged a $350 million gift to Johns Hopkins University to support interdisciplinary research and student financial aid, a commitment that will push his lifetime donations to his alma mater to more than $1 billion, the university announced Saturday.

Hopkins officials said they believe that Bloomberg will become the first person to reach the $1 billion level of giving to a single U.S. institution of higher education — an assertion that’s hard to verify because many donors give anonymously to universities. It is also difficult to compare the dollar value of modern donations to those in earlier eras.

But Bloomberg’s philanthropy to Hopkins is by any reckoning remarkable. A list of major higher-education gifts compiled by the Chronicle of Higher Education in 2012 was topped by a $1 billion commitment for scholarships from the Bill & Melinda Gates Foundation.

Bloomberg’s first gift to Hopkins was $5 in 1965, a year after he graduated from the private Baltimore university with a bachelor’s degree in engineering. His first $1 million pledge to Hopkins came in 1984, endowing a professorship in the humanities.

Now the 70-year-old billionaire, who made a fortune in the financial information business, has pledged $250 million to promote research in water resource sustainability, individualized health care delivery, global health, the science of learning and urban revitalization. In addition, he has pledged $100 million for scholarships to aid undergraduate students in financial need. The combined commitment of $350 million — the largest gift ever to the university — will bring his lifetime donations to Hopkins to $1.118 billion.

New York City Mayor Michael Bloomberg speaks at a gun violence summit at Johns Hopkins Bloomberg School of Public Health in Baltimore, on Jan. 14, 2013. (Patrick Semansky/AP)

“Each dollar I have given has been well-spent improving the institution and, just as importantly, making its education available to students who might otherwise not be able to afford it,” Bloomberg said in a statement issued through the university. “Giving is only meaningful if the money will make a difference in people’s lives, and I know of no other institution that can make a bigger difference in lives around the world through its groundbreaking research — especially in the field of public health.”

Hopkins President Ronald J. Daniels called Bloomberg a “force for social good” who ranks among philanthropists such as Andrew Carnegie, John D. Rockefeller and the university’s namesake, the 19th-century Baltimore merchant Johns Hopkins.

“It is simply an extraordinary level of philanthropy,” Daniels said in a telephone interview Saturday. “It goes right to the core of the academic enterprise. It’s a magnificent gift. What can I say?”

The mayor’s gift will endow 50 faculty positions to be called “Bloomberg distinguished professors,” all of them based in more than one school within the university. That builds on a trend in higher education to facilitate research that crosses disciplines that have long been isolated within academia. Neuroscience, for example, might have much to contribute to education research. But until recently, universities have built few bridges to encourage teamwork in those fields. Georgetown University in November announced a $20 million gift to spur interdisciplinary research in environmental studies, using the same logic behind the Hopkins initiative.

Daniels said that Hopkins faculty and deans spent the better part of two years brainstorming about interdisciplinary projects, considering some proposals and rejecting others. The university settled on several targeted areas of inquiry. Then Daniels took a proposal to Bloomberg, meeting with the mayor at New York City Hall on June 25.

Bloomberg, Daniels said, peppered him with questions: How would it work? How would you recruit faculty? How would you know the schools are really committed to these kinds of collaborations? The mayor, from long experience in business and politics, knew that academic silos could prove as difficult to break down as those that hinder cooperation among government agencies.

Phone calls ensued as Bloomberg’s interest grew.

In August, the mayor tracked down Daniels in Florence, Italy, to talk about the potential gift. The Hopkins president told Bloomberg that his generosity toward the university brought to mind how a political dynasty of centuries ago had supported the Italian Renaissance in art.

“You are the Hopkins Medici,” Daniels told him.

Bloomberg, Daniels said, agreed to make the pledge in a fall meeting in New York.

Bloomberg already is an icon at Hopkins. His name is on the Bloomberg School of Public Health and the Bloomberg Center for Physics and Astronomy. His mother’s name is on the Charlotte R. Bloomberg Children’s Center at Johns Hopkins Hospital. He has funded a plethora of campus renovations and research on malaria, gun violence prevention — one of his political priorities — and numerous other topics.

Daniels said Bloomberg, unlike some higher education donors, has not sought to impose an agenda on the university. “He is totally devoted to our mission,” he said.

New York journalist Joyce Purnick, author of a 2009 biography of Bloomberg, wrote that he had middling grades as a high school student but got SAT scores strong enough to help him get into Hopkins. As it turned out, whoever decided to admit him made the right call.

“You know,” Bloomberg told Purnick, “there’s a joke at Johns Hopkins: They’re going to put up three statues — one of Johns Hopkins, one of me — and one of the admissions officer.”