D'Antona leaves in March to launch an as yet unnamed PR consultancy to be based in Italy. She said she is in negotiations with Edelman over the transfer of a handful of clients to the new firm.
D'Antona said: 'After 12 years with the company and having contributed to the unification of Edelman Europe, I thought it was a cycle that was over.'
She added the agency will 'provide a mix of corporate PR through to promotion work'.
The move comes 12 years after D'Antona sold her original agency Gruppo D'Relazioni Pubbliche to Edelman - which also saw D'Antona become general manager of the network's Milan office. She was promoted to head Edelman Europe in July 1999 with a remit to lead the firm's 12 offices across the region.
Edelman is not directly replacing D'Antona, instead handing her responsibilities to president of international operations Alison Canning.
Canning adds the brief to her existing remit to oversee areas including Latin America, Canada, Europe and Asia.
- Edelman's Dublin office general manager Hugh Gillanders has taken the post of chairman at the Irish arm of the PRCA.
He succeeded John Saunders, managing director of Fleishman-Hillard Saunders, at the association's AGM last month. Gillanders takes the post after a year as vice-chair.