A large bronze statue of a hare was stolen from a trade stand at Badminton Horse Trials, Avon and Somerset Police said.
The statue, which is on a hamstone base and measures 135cm in height, was made by Somerset artist Jan Sweeny and is valued at £19,000.
The Badminton Horse Trials is a five-day event that takes place in April or May each year in the park of Badminton House, the seat of the Duke of Beaufort in south Gloucestershire.
Pc Matt Leigh said: “Being bronze, the statue weighs a considerable amount and so it’s likely more than one person was involved in removing it from the trade stand it was on display at.
“We’re keen to hear from anyone who may have seen it being removed or transported and are also asking those at Badminton today to keep an eye out for it.
“If you have information which could help us recover the statue and find those responsible for the theft, please call 101 and provide the call handler with the reference 5222108421.”