The monument recalls commandos who trained in the area in wartime.
A donation box has been stolen from the commando war memorial at Spean Bridge in Lochaber.
Northern Constabulary area commander John Chisholm described the incident as "sickening", particularly coming so close to Remembrance Sunday.
It was not known how much money was in the box, but police said usually gifts increased around 11 November.
The memorial and its statues are a tribute to commandos who trained in Lochaber during World War II.
Ch Insp Chisolm said: "This venue is recognised the world over and it is particularly distressing that a crime such as this takes place on the approach to the annual festival of remembrance."
In 2006, a Royal Marine upset by the state of a garden of remembrance near the memorial led efforts to refurbish it.
Commando Ali McGill and 19 volunteers from the Fleet Protection Group at HM Naval Base Clyde worked on the project.