Brian Chesky, CEO of Airbnb, announces a $100 million donation to support San Francisco parks at a press conference with Mayor Daniel Lurie at the Conservatory of Flowers in San Francisco.

Weston Turtle Fudge/S.F. Chronicle

San Francisco is getting a $100 million gift from a tech billionaire to improve public parks in what Mayor Daniel Lurie ’s administration says will be the largest contribution the city has ever received from a single donor.

Airbnb CEO Brian Chesky is committing the funds, which will be delivered in two phases, the city announced Monday. The first $39 million will help San Francisco finish five park projects in the South of Market, Bayview-Hunters Point, the Mission, Potrero Hill and downtown. City parks officials will spend a year figuring out how to best use the remaining $61 million from Chesky.

The money represents a major escalation of Lurie’s efforts to supplement the work of his administration with funding from the private sector .…