The safe installation of the 6,500 tonne structure by the deepwater construction vessel Aegir marks the beginning of the Project's major installation campaign in the Browse Basin, offshore Western Australia.
Ichthys LNG Project Managing Director Louis Bon said the RSS is the largest subsea structure ever laid on the seabed.
'The Riser Support Structure is the masterpiece of the Project's subsea facilities,' Mr Bon said.
'It is also a serious physical foundation, because when its arch is placed, the structure will stand 110 metres off the seabed.
'Today's milestone is significant for the Project, because it marks our return to the Ichthys Field for the installation of our offshore facilities after years of intense engineering and fabrication work.'