He was from the fifth crop of his sire Positano (GB) and was the fifth foal of his dam Jacinth, a daughter of Martini-Henry (NZ), winner of 1883 VRC Melbourne Cup.

[2] At the dispersal of the Neotsfield Stud, Poseidon was sold to the Moses brothers as a foal at foot with his dam for 400 guineas.

Interested only in the dam and not the foal at foot, Poseidon was later sold to owner, Sir Hugh Denison for 500 guineas at the April 1905 Chisholm and Co Yearling Sales in Sydney.

Just two days later, he raced against older competition for the first time in the AJC Metropolitan Handicap, finishing in second place to Solution (NZ).

He then finished second to Dividend in the three mile VRC Champion Stakes, before heading back to Sydney for the Autumn Racing Carnival.

At his second start Poseidon disappointed his backers with a poor third in the AJC Craven Plate, after Antonius had cannoned into him mid-race and knocked the wind out of him.

On Derby Day, as 1-3 favourite, Poseidon won again beating Apologue in the VRC Melbourne Stakes.

The weight told, and Poseidon finished in eighth place with the win going to Apologue who carried only 7 st 9 lb (49 kg).

As he would require a long spell away from the track to recover, the decision was made to retire Poseidon to stud duties.

Each year the Listed VRC Poseidon Stakes for three-year-old colts and geldings is run in his honour.