Australis ships sail through the Chilean-Argentinean Patagonia region in South America.
Four Travel has been appointed to promote the line's voyages to consumers, the travel trade and broader media with the aim of raising awareness of the brand and product offering.
The agency will also focus on activity that generates coverage and awareness in the run-up to the 500th anniversary of the first recorded circumnavigation of the world by Portuguese explorer Ferdinand Magellan.
Australis UK and Ireland sales and business development manager Silvia Vizzoni said the business was "delighted" to be working with Four Communications.
"They demonstrated their extensive experience of working within the travel industry and I am sure will help us further raise our profile and develop our presence [in] UK and Irish markets," Vizzoni said.
Helen Coop, Four Travel’s head of PR, added: "As the demand for special-interest tourism grows, we are delighted to be working with Australis, a leading expedition cruise company well known for conducting its operations in a sustainable way.
"This is an exciting addition to our portfolio and we look forward to a successful working relationship."