Pleas to return the Sandown Illuminated Carnival banner have been posted to social media.
The banner which has been described as “not cheap” went missing from railings on Sunday (August 5) in Battery Gardens, Sandown.
Another banner for Sandown Regatta also went missing from the park at around the same time.
A spokesman for Sandown Illuminated Carnival said: “If anyone knows of the whereabouts of a Sandown Carnival banner that looks like this, please let us know.
“It was stolen last night from the railings at Battery Gardens Sandown, along with a white Sandown Regatta banner. These banners are not cheap and neither event can afford to keep replacing them.”
Hampshire Constabulary have been approached for comment.