Harding will conduct Idomeneo on the company's opening night in December.
In a press conference on July 21, La Scala general director St_phane Lissner said that the opera company would begin a new direction, a "fresh artistic impulse."
Muti, who directed La Scala's orchestra for 19 years, resigned in April, following a long standoff with musicians and La Scala employees who were angry about what they felt to be his part in the firing of then-general manager Carlo Fontana.
"You don't replace Muti in a month or in a year," Lissner said. "It's impossible to replace a conductor of his ability. If a replacement exists, he's not available."
Lissner also said that his priorities for La Scala are to "give back the sense of a big artistic impulse, get back to economic rigor, and ensure social cohesion in the house."