Optus has selected Arianespace to orbit its D3 satellite in 2009.
Known as Optus D3, it will be orbited by an Ariane launcher or a Soyuz launcher from Europe's Spaceport in French Guiana.
It is the fifth satellite launched by Arianespace on behalf of Optus.
Arianespace launched Optus D1 in October 2006, after Optus & Defence C1 in 2003 and Aussat A3 in 1987.
Optus D2 is scheduled for launch by Arianespace later this year.
Optus' parent company SingTel also chose Arianespace to launch its ST-1 satellite in 1998.
American satellite manufacturer Orbital Sciences Corporation will construct the Optus D3 using the Star-2 platform.
The satellite will weigh about 2,500 kg at launch, and will be positioned at 156 degrees East.
Offering a design life of 15 years, the satellite will provide direct TV broadcast, Internet, telephony and data transmission services for Australia and New Zealand.
Optus D3 is the 285th contract signed by Arianespace since its founding in March 1980.
Arianespace currently has a backlog of 41 satellites to be launched.