The opening of the New York Philharmonic’s 174th season on Thursday felt like the start of a new chapter, as the orchestra played for the first time in the newly rechristened David Geffen Hall and announced that it was getting the largest individual donation in its history: a $25 million gift from Oscar S. Schafer, the chairman of its board, and his wife, Didi.

The gift provided an extra fanfare to begin the season, and signaled that the Philharmonic was addressing the biggest challenges it has faced in decades, including raising its share of the costs to renovate its hall; shoring up its finances; and finding a new music director to succeed Alan Gilbert when he steps down in 2017.

Mr. Schafer — a financier who with his wife has sponsored the Philharmonic’s free concerts in city parks since 2007 and who became its chairman this year — said he hoped his gift would inspire donations from fellow board members and others.

“I’m trying to set the standard that it’s an important obligation of the board, and not only the board but people in and around New York — because it is the New York Philharmonic,” Mr. Schafer, the founder of the Rivulet Capital investment firm, said in a telephone interview. “The New York Philharmonic is revered throughout the world, but sometimes is taken for granted in New York.”