She replaces joint presidents Sue Hardwick and Angela Oakes, who have stood down. Other new board members are Shelley Facius of Bell Pottinger and Nicola Hyde of Instinctif Partners.
Whenman said: "Promoting better balance in the boardroom and supporting the female pipeline is essential if the public relations industry is to grow and thrive. While there are some great examples of best practice, there is still work to be done.
"My number one priority is to grow WPR’s membership, so that it represents the diversity of senior women operating across our industry. I am looking forward to building on the great work of my predecessors Sue Hardwick and Angela Oakes, while bringing new ideas to the group with the support of the WPR committee."
Francis Ingham, director general of the PRCA, said: "Over the past two years Sue and Angela have spearheaded the revival of the organisation and have worked tremendously hard to turn WPR into the strong and vibrant organisation it is today. I have very much enjoyed working closely with both of them and thank them for their tremendous enthusiasm and dedication. I look forward to welcoming Mary as president."