Glentoran Marcus was a top pedigree Jersey-breed bull who won 30 Jersey championships and Dairy All-breed championships in New Zealand during the early 1960's.

He was bred by an Irish immigrant, John Campbell Armstrong, founder of the Glentoran Jersey cattle stud in the Waikato.

Coming from Northern Ireland, J C Armstrong had affiliations with the Glentoran Football Club, which provided him with the name of his cattle stud farm.

Numerous bulls were award winners at Agricultural and Pastoral shows in New Zealand, the most prolific winner being national champion, Glentoran Marcus.

Sean Armstrong, grandson of John Campbell Armstrong, is the founder and Managing Director of Glentoran Software.