Ursula Lidbetter, who is also the chief executive officer of Lincolnshire Co-op, left the post at the end of 2019.
The LEP is a business-led partnership of private and public-sector figures.
It works with business, the Government and local authorities to drive economic growth across its patch.
Directors can serve for a maximum of nine years and Ursula has been leading the organisation since it launched in 2010.
She said it had been a ‘privilege’ to serve as chairman in that time, adding: “The difference we’ve made can be seen from the Humber to the Wash in better infrastructure, innovation and business growth, university and college provision.”
Until an appointment is made, the LEP’s deputy chairman Pat Doody will act as interim chairman.
“I know I speak for the rest of the board when I reflect that Ursula has provided a very clear sense of direction and purpose to the LEP’s workings and has always had the best interests of Greater Lincolnshire at the heart of decision making,” said Pat.