The passing of Karl Lagerfeld presents Chanel with its biggest creative challenge since the death of its iconic founder almost half a century ago.

Since 1983, Lagerfeld reigned over Chanel with indisputable authority, helping turn a storied haute-couture fashion house into a global megabrand with $9.6 billion in annual sales. His death, at the age of 85, has left long-time creative deputy Virginie Viard in charge of the collections.

Crucial to the future of the closely held brand is whether Viard can emerge from Lagerfeld’s shadow and impose a convincing vision, or whether Chanel will seek an established outsider such as Phoebe Philo, who left LVMH’s Celine last year after a decade, or Alber Elbaz, formerly of Lanvin.

“They will look for a high-profile chief creative officer, and in the meantime they have got incredibly capable people in their team,” said Mario Ortelli, who runs a London-based advisory firm on luxury strategy. “Any designer in the world would be more than delighted to work with Chanel.”

‘Creative Genius’

Lagerfeld oversaw as many as eight Chanel collections a year: spring, fall, skiwear, haute couture, and more. One of fashion’s most prolific couturiers, he also produced outfits for Italy’s Fendi SpA and his own label. Recognizable for his high-collared shirts, white ponytail, dark sunglasses and black fingerless gloves, Lagerfeld had a client list that featured stars of the stage and screen, including actress Cate Blanchett and singer Pharrell Williams.

“We have lost a creative genius who helped to make Paris the fashion capital of the world,’’ Bernard Arnault, the chairman and chief executive officer of luxury giant LVMH Moet Hennessy Louis Vuitton, said in a statement.

When Chanel last month said the designer was too tired to appear at his spring-summer haute couture show in Paris, his absence made more news than the hand-stitched floral gowns, sequined tweed suits, and feather capes on the catwalk. Conversation quickly turned to what Chanel planned to do next.

The fashion house said that Viard, his “closest collaborator for more than 30 years,’’ has been entrusted with the creative work on the collections, “so that the legacy of Gabrielle Chanel and Karl Lagerfeld can live on.’’

Fashion house Fendi said it’s too soon to discuss Lagerfeld’s succession. “We intend to take the time to honor his life and pay him the tribute…