The item, described by producers as “a world famous piece owned by a sporting institution”, was discovered in North Yorkshire. It is worth more than £1m (€1.4m).
According to the BBC, this breaks the record for the previous holder of the title, a model of Antony Gormley’s Angel Of The North, which was valued at £1m in 2008.
The exact valuation of the record-breaking item has not yet been revealed. The episode will air in April.
A spokesman for the show, presented by Fiona Bruce, said: “An item seen at the Antiques Roadshow in Harrogate is the highest valued object ever to appear on the show in its 38-year history.
“It is a world-famous piece owned by a sporting institution. The final valuation given will be revealed when the programme airs in spring 2016.”