"TG is embarking on new career and business pursuits that requires his full attention," said a club statement.
"Given constraints of time and distance, TG believes he is unable to meet the demands of his position as chairman and board member of Cardiff City Football Club.
"We are greatly indebted to TG who since joining in 2010 has been instrumental in the progress of the club to where it is today, and we wish to record our deep appreciation for his invaluable contributions and efforts."
TG has been chairman since 2010 and introduced business partner Vincent Tan to the Bluebirds.