He succeeds George Mayhew, who is leaving National Grid after 12 years.
Wyld, who featured in PRWeek’s Power Book, joined Rolls-Royce in July 2017 and has also held senior comms roles at Network Rail, where he was group communications director, Unilever and the Office of Fair Trading.
He officially joins National grid on 15 October and will report to CEO John Pettigrew. Wyld will also sit on the group executive committee – a reflection of the growing importance of corporate affairs to business.
"I want to thank George for his hard work and dedication and the influence he has personally brought to bear in cementing our strong reputation in the UK and the US," Pettigrew said.
"He played a pivotal role in embedding the company’s purpose, vision and values and was a great support to me when I became CEO in 2016.
"Barney has a great track record of leading corporate affairs teams and defining and delivering communications strategies for large organisations, and we are excited to welcome him to the company."
Yesterday, new research by executive recruitment firm Odgers Berndtson found a growing proportion of FTSE 100 corporate affairs leaders were on remuneration packages of more than £500,000, with an increasing number reporting directly to the CEO.