Medley is currently MD at Spider PR, formerly The SPA Way. He will take up his new position on 1 February.
Before Spider PR he was MD of Publicis Consultants, following senior stints at GCI and Porter Novelli.
He takes over the role from Nexus chairman Jonathan Choat, who is also currently MD. Choat said: 'I am delighted that Richard is joining Nexus.
'His skills and enthusiasm are the perfect fit for us and I am certain that he will play a crucial role in taking the company forward to meet the challenges and opportunities of the changing PR landscape.'
Medley added: 'With strong heritage and established expertise to build on, multiple awards for creativity, and an enviable business model in place, it’s not difficult to see the appeal of Nexus as an agency well set for the future, and one brimming with ambition that I want to help deliver.'