Guards realised that the gatecrasher joined the models when it was too late to intervene.

A gatecrasher jumped onto the catwalk at Chanel's Paris fashion week show Tuesday and walked unchecked with the models for the big finale.

The woman, a guest at the show, ran down from her seat and joined the models as they did their last walk along a spectacular set recreating the roofs of Paris inside the Grand Palais.

With security guards left floundering, supermodel Gigi Hadid eventually confronted the gatecrasher as she tried to further upstage the models, and escorted her off the set.

The daring infiltrator was dressed from head to toe in a black and white Chanel-like tweed suit and hat, and slipped unnoticed onto the catwalk.

Guards only realised that she had joined the models when it was too late to intervene.

"I couldn't stop laughing because the hapless security guards couldn't spot her in the line-up," said the New York Times' Elizabeth Paton.

By then the woman -- who has yet to be identified -- was giving it her all, waddling down the catwalk with her hands on her hips like a supermodel.

Moments later as the women left the line of models to pose further up on the rooftop, Hadid stood in her way and a brief face-off followed, before the model escorted the smiling woman offstage.

Chanel told AFP that the woman had taken them by complete surprise but that "this is not the first time that she has done this."

Models didn't miss a step

The same woman may also had gatecrashed a show by the lingerie brand Etam last week.

"We are not going to make a drama out of it," a Chanel spokeswoman added.

"We would have preferred if it hadn't happened."

The woman was "escorted to the exit by our security personnel afterwards."

The models -- which included the Gigi Hadid's sister Bella -- did not miss a step as they made space for the gatecrasher as they filed backstage.

It was only as the woman doubled back that Hadid acted.

Most of the hundreds of fashionistas at the show did not realise what had happened as they clapped or filmed the finale with their smartphones.

With the front row crammed with celebrities from US rapper Cardi B to K-pop star Jennie and French actress Isabelle Adjani, security had been tight, but guards were left trailing in the lady's wake.

Chanel designer Virginie Viard had turned the clock back in her spring summer show, with a battalion of models channelling the insouciant sophistication of 1960s socialites.

Like several Paris shows over the last nine days it was marked by a strong return to femininity after several seasons when androgyny ruled the catwalks.

With its copious references to the French capital, like Celine and Saint Laurent shows before, Chanel also paid homage to the city's style tribes of the 1960s and 1970s.

Viard took over the iconic French brand in February days after the death of its legendary designer Karl Lagerfeld.