Constantine, the former marketing director of News International's The Times and The Sunday Times, takes up the newly created role with responsibility for global consumer and business marketing of Metro.
He will co-ordinate Metro's marketing across its European, American and Asian regions, implementing group-wide initiatives to promote its global strength while heading research into both local and international readership.
Metro is the world's largest newspaper brand outside of Japan, with 28 editions that attract more than 12 million daily readers in more than 16 countries.
However, Metro in the UK, owned by Associated Newspapers, is not one of its properties.
Constantine said: "My job is to establish a fully formed marketing function across the network to maximise the enormous potential of the Metro brand to readers and advertisers. It's an exciting opportunity."