Yale University received a $250 million pledge, the largest gift in its 312-year history, from alumnus Charles B. Johnson to build two new colleges.

The donation will help Yale increase its residential colleges to 14 and expand its undergraduate student body by about 15 percent to more than 6,000, the university in New Haven, Connecticut, said today in a statement. Yale needs an additional $80 million to break ground on the colleges, the school said.

Johnson, 80, who played football at Yale before graduating in 1954, retired last year as chairman of Franklin Resources Inc., a San Mateo, California-based money manager. Johnson, who joined the company in 1957 at age 24, has a personal fortune worth $2.4 billion, according to data from the Bloomberg Billionaires Index. Johnson’s previous gifts to Yale include funds to renovate the football stadium, and to establish the Johnson Center for the Study of American Diplomacy, which holds the papers of Henry Kissinger.

“This is an extraordinary commitment from one of Yale’s most loyal alumni,” Yale President Peter Salovey said in the statement. “It builds on Charlie’s long history of generosity to Yale. Charlie has already done so much to shape our international and athletics programs.”