The 24-year-old striker finished as the top scorer in Austria's top flight last season with 17 goals in 33 games.
Kayode had been linked with a move to Newcastle United.
Four other City players are to spend the 2017-18 season at newly-promoted La Liga side Girona.
Brazilian £10.7m midfielder Douglas Luiz, right-back Pablo Maffeo, midfielder Aleix Garcia and Colombian winger Marlos Moreno have all signed loan deals with the Spanish club.
Girona have officially confirmed the loan deal for Kayode, but City are yet to make a formal announcement.
He scored 24 goals in 48 matches for Vienna last season, including two goals in two games against Roma in the Europa League.
Kayode, who has also played for ASEC Mimosas in the Ivory Coast, FC Luzern in Switzerland Maccabi Netanya in Israel. He represented Nigeria at the 2009 and 2011 Under-17 and Under-20 World Cups respectively.
He made his debut for Nigeria in a friendly against Senegal in March and has three caps for the three-time African champions.
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Manchester City have signed Nigeria international Olarenwaju Kayode from Austria Vienna on a four-year deal and sent him on a season-long loan to Spanish side Girona.