Kay joins from ad agency Fallon, where he worked as head of account management, and replaces former marketing director Matt Lowery, who left two months ago.
He will report into the club's brand and marketing officer David Pullan, who joined from media planning and buying group Aegis in March. Kay takes up his position next month.
The new head of marketing said he will use advertising and commercial partnerships with the aim of making Manchester City one of the ‘biggest football brands in the world'.
Manchester City, the world's wealthiest club, recently announced a kit deal with Umbro and shirt sponsorship deal with Etihad, which is worth an estimate £40m.