Jerry O'Sullivan has been appointed deputy chief executive at the ESB.
Mr O'Sullivan will take up the role at the end of September, replacing Brid Horan who has been Deputy Chief Executive since May 2013.
Welcoming the appointment, Pat O'Doherty, chief executive of ESB, said:
"Jerry O'Sullivan is an immensely experienced and respected member of ESB's leadership team. I look forward to working with Jerry over the coming years as ESB continues to bring sustainable and competitive energy solutions to all our customers."
Mr O'Sullivan was appointed Managing Director of ESB Networks in 2010. Prior to that he held a range of senior executive positions in the company. He joined ESB in 1981.