Click here to see the video. OPEC is the Organisation of Petroleum Exporting Countries.
Mr Bush, who flew halfway around the world to be in Australia, not Austria, for the APEC (Asia-Pacific Economic Cooperation) summit of world leaders, took to the stage at the Sydney Opera House.
He thanked Mr Howard for his introduction and for being such a "kind host" for the OPEC summit.
"I mean APEC summit," he said.
"I've been invited to the OPEC summit next year. The APEC summit."
The faux pas brought laughter from his audience.