One by one, the ballerinas of New York City Ballet made their grand entrances in “Bal de Couture,” a new work by Peter Martins, and the glittery crowd applauded in delight. But the applause, this time, wasn’t for the dancers.

It was for the costumes.

You might have thought Fashion Week at Lincoln Centre was already over. But last Thursday night, on the same plaza where models had strutted the runways just days earlier, it seemed like that had been a mere prelude to NYCB’s glittery fall gala. The evening’s star was legendary designer Valentino, and the focus was on clothes, onstage and off.

And they were pretty cool clothes: Designer gowns in the audience, of course, many of them in Valentino’s signature red, but truly dramatic concoctions onstage: flouncy dresses in layers and layers of black and white tulle, for example, revealing a surprise under-layer of bright red or pink, like red bloomers on a can-can girl.

Or a one-shoulder ballgown covered with rosettes, all in ruby red. Or sculpted, bubble-shaped tutus with tight bodices, in black, white, and, of course, red.

Valentino, whose full name is Valentino Garavani, is now 80, a statesman of the fashion world. He retired nearly four years ago from the fashion house he founded in 1960.

But one of his most loyal celebrity fans, Sarah Jessica Parker, a board member of City Ballet, came up with the idea of a collaboration for the fall gala. It didn’t hurt that Valentino was a longtime friend of Martins, City Ballet’s master in chief. Fashion, the company clearly reasoned, could be a way to connect with younger audiences.

It wasn’t the first time City Ballet has reached out to top designers” the last gala, in the spring, was a French-themed evening featuring costumes by Gilles Mendel, of the J. Mendel label. And last spring’s gala featured “Ocean’s Kingdom,” with music by one Paul McCartney. The costume designer? His designer daughter Stella, of course.

But Thursday’s gala was the company’s most sweeping ode to fashion yet. In the crowd, along with Parker, were other famous fans like actress Anjelica Huston, model Iman, actress Anne Hathaway, and Martha Stewart. A number of ballet patrons wore Valentino, sometimes with accompanying rubies and diamonds.

Speaking of “Rubies,” that Balanchine classic — the middle section of his famous “Jewels” — was the only ballet performed Thursday that Valentino didn’t design for. Its well-known red costumes are by Karinska, and its inclusion was a clear tribute to the designer.

The evening began with two new ballets created by Martins. In “Sophisticated Lady,” to music by Duke Ellington, Maria Kowroski glided ballroom-style around the stage with a contingent of tuxedo-clad men, 17 to be exact, led by the suave (and recently retired) Charles Askegard. The dancing was pleasant but the focal point was clear: Kowroski’s fabulous red, one-shoulder Valentino gown. (Hopefully, she recycled it later for the evening’s gala dinner.)

Another new Martins work followed, “Not My Girl” to music by Fred Astaire and Van Phillips, notable for the tapping of Robert Fairchild and the bright, engaging dancing of Tiler Peck in a frothy pink-and-red Valentino tutu.

The best dancing by far, though, came in the lovely and heartbreaking new pas de deux by Christopher Wheeldon, “This Bitter Earth,” to music by Max Richter and Dina Washington. It was a preview of Wheeldon’s new ballet, “Five Movements, Three Repeats,” and though there are no immediate plans for City Ballet to perform it again, it was the highlight of the night for those who came for dance. Whelan remains a wonderful muse for the hugely gifted Wheeldon, her every move conveying meaning, purpose and feeling.

The evening would end with a sumptuous dinner on the promenade of the David H. Koch Theater, where tables were decked with pink tablecloths and bright red flowers, with red sashes crisscrossing the room overhead.

But first came the true fashion show of the night, Martins’ “Bal de Couture,” with those tulle-filled creations. Afterward, the crowd stood — but only when Valentino came out for his bows.