The US marketing chief will report to Terri Westlake who has been made global marketing director on a permanent basis after taking the interim job in March. Asos is currently recruiting to fill the US role.
Asos hopes to build brand awareness and increase traffic and sales in the US after launching there two years ago.
The US marketing director will be responsible for digital marketing, CRM activity, advertising, ecommerce, editorial content and PR in the region as well as providing local insight for the global teams based in London.
They will work alongside Matt Hiscock, current director of international sales, who will move to the US as country manager to head up the operation.
Asos introduced its first regional marketing teams overseas earlier this year in recognition of the need to service its rapidly expanding international business with localised marketing teams. Previously all marketing was led from the UK office.
Offices were set up in Australia and planned for other countries where Asos operates such as France and Germany, but it has no director level marketers outside of the UK.
Asos has set the target of reaching £1bn annual sales by 2015 and hopes that increasing its marketing clout in new regions will help achieve this. It registered global sales of £481.5m in the year ending 31 March 2012.
Almost 60% of Asos revenue comes from international sales, but the majority of its 900 staff are currently based in the UK.
Asos claims to be the third most visited clothing website on the planet, attracting 17.5 million unique visits a month and 4.4 million active customers in 160 countries.