Mayor Bill de Blasio on Monday attended his first COVID-19 vaccination — which was administered at a private as opposed to city-run hospital.

The mayor witnessed the inoculation of an ICU nurse at NYU Langone Health in Manhattan, calling the vaccinations that began in several hospitals across the city “a beautiful moment.

“This will be one for the ages,’’ Hizzoner said of what he described as “the greatest vaccination effort ever in the history of New York City.’’

Those in the room began clapping when the shot was administered.