A Swiss tourist has been missing for a week after heading out on a fishing trip near Arthur's Pass in the South Island.

Gregoire 'Greg' Bornand has not been seen since March 7 when he left his car at the Poulter River car park, near Mount White Station.

Police believe he was going on a fishing trip and was due to return on March 9.

A search and rescue helicopter has been searching the river, track and local Department of Conservation huts this afternoon.

Bornand has been in New Zealand since October 2016 and is thought to be here on holiday.

Anyone who may have seen him fishing or travelling in the area is asked to contact police, quoting reference number P028839530.