Markey, who leaves insurer RSA after eight years at the group, will bring his extensive financial services experience to bear at the Post Office, which is increasingly active in the marketplace.
He will report to Martin George, the Post Office’s chief commercial officer, who joined the organisation last year.
Markey, who will start his new role in May, told Marketing that he was excited about working for such an "iconic brand with a strong retail presence and strong portfolio of products". He also described George as an "inspirational" leader.
He said: "What’s interesting is that the Post Office’s product range stretches across the board – from telecoms, to financial services, such as credit cards and banking. There are a number of product types that I’ve worked on and a number that I haven’t.
"The Post Office has 11,500 retail outlets, so that will be an exciting challenge."
George added: "We are absolutely delighted to welcome Pete to the team. We are transforming the Post Office into a multi-channel, commercially viable retailer. Pete’s first-class FTSE 100 experience will help drive develop our ambitious brand and marketing strategy to deliver these commercial objectives."
Markey added: "I look forward to elevating the Post Office brand to achieve its ambition of becoming a multichannel retailer that will meet the changing needs of its customers."
Markey, a previous winner of The Marketing Society’s Leader of the Year award, has been RSA’s top global marketer for two years.
The former More Th>n marketing director is a well-known networker on the marketing scene and often seen speaking at industry events.
Before joining RSA’s More Th>n in 2006, he held posts including marketing communications manager of AA and direct marketing manager of British Gas.
It is not yet known who will replace Markey at RSA, although the most obvious internal candidate as successor would be Dominic Grounsell, RSA’s personal marketing director, who currently reports to Markey.