Taylor, who is currently head of public affairs at the supermarket chain, will take up her new role on 1 February 2016.
She has worked for Sainsbury's for 13 years in various comms roles. According to LinkedIn, she started her career in the Conservative Party press office, before working for agencies Porter Novelli and Rock Communications.
Taylor succeeds Louise Cooper, who was with John Lewis since 2006, and was head of external comms since May 2014. She has opted not to return from maternity leave, and has started her own consultancy specialising in supporting fast-growth businesses, according to a John Lewis spokeswoman.
Taylor will report to comms director Peter Cross, who said: "Gillian masters all aspects of the craft and has genuine hands-on retail experience. I know she will bring a huge amount to our brand and our team."
Pending Taylor's arrival David Sawday, former director of group comms at Carphone Warehouse, will join John Lewis on an interim basis as it gears up for the Christmas period. Sawday starts on Monday (5 October).
A spokeswoman for Carphone Warehouse said Sawday had left the firm earlier in the year and that it had not hired a direct successor, due to the comms team's structure changing following the 2014 merger of Carphone Warehouse and Dixons Retail, which created Dixons Carphone.
John Lewis, which fared well in a recent PRWeek-commissioned YouGov survey of the UK's most trusted companies, earlier this year appointed its first dedicated corporate comms agency.