The shindig held Monday night at The Metropolitan Museum of Art raised an astonishing $15 million ... this according to a Met rep. That's a jump from last year's $13M figure. The Met Gala is the museum's main source of annual funding for exhibitions, publications, acquisitions and capital improvements.

The stars didn't disappoint this year. Lady Gaga strutted into the event with a giant pink Brandon Maxwell dress and she was barely getting started when a small army helped her make her way in. As we reported ... Lady Gaga had several wardrobe changes and nearly stripped down to her birthday suit.

Gaga -- along with Harry Styles, Serena Williams and Vogue editor-in-chief Anna Wintour -- co-chaired the evening. This year's theme was dubbed "Camp: Notes on Fashion" to honor writer Susan Sontag's 1964 essay, "Notes on Camp" about society broadening its attitudes toward sexuality ... particularly homosexuality.

The Gala's been going down since 1948 but it wasn't until former Vogue editor Diana Vreeland became a consultant and transformed it into a glamorous affair. Vreeland's first theme in 1973 was "The World of Balenciaga."