Marguerite Sayers has been appointed Deputy Chief Executive of the ESB Group.
Ms Sayers succeeds Jerry O'Sullivan who is retiring following 41 years with the organisation.
Meanwhile, Pat Fenlon took up his new role as Executive Director, Customer Solutions in September and Paul Stapleton was appointed Executive Director, Group Finance and Commercial from early October.
ESB Chief Executive Paddy Hayes said that Marguerite, Pat and Paul all bring considerable experience and capability as well as a record of delivery.
"They assume their new roles at a time of great change, as the energy sector confronts the challenges of decarbonisation, security and affordability," he added.
Marguerite Sayers joined ESB in 1991 and in recent years, she has held the position of Executive Director, Customer Solutions and Managing Director of ESB Networks Ltd.
Pat Fenlon replaces Marguerite as Executive Director of ESB's Customer Solutions business, which includes Electric Ireland, So Energy, ESB ecars and ESB Smart Energy Services.
And Paul Stapleton replaces Pat as Executive Director, Group Finance and Commercial. He is a former Managing Director of Northern Ireland Electricity Networks, an independent subsidiary of ESB.
