Eden Project executive director Gaynor Coley is leaving the Cornwall attraction to join the Royal Botanic Gardens, Kew, as director of public programmes.
Ms Coley joined Eden in 1997 and led the financing of the £141.4m project. Once it was operational, she became managing director with responsibility for operations, finance and education.
During her time in charge, Eden has welcomed more than 14 million visitors and won Best UK Leisure Attraction at the British Travel Awards in 2011 and 2012. In 2009 she received the CBI Real Business First Women Award in tourism and leisure.
She will take up her new post at Kew in the autumn.
Judith Donovan, non-executive chairman of Eden Project Ltd, said: "This is a fantastic opportunity for Gaynor. We all wish her well. She will be sorely missed at Eden."
Marcus Agius, chairman of trustees at Kew, added: "We look forward to this strengthening the working relationship between Kew and Eden."