The antique four-poster with its ornate carved headboard was built for the residents of the Berkeley Castle estate in Gloucestershire in 1608 and has been used for more than 400 years.
It has been providing a "comfortable" night's rest for the couple at Gloucestershire Castle, 'The Telegraph' reported.
The style of the bed posts date them to the period 1560-1640, say Furniture historians.
They believe the royal arms in the middle of the headboard are of the Stuart monarchy, dating the bed more specifically to the period after the accession of James I in 1603.
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The bed was identified by retailer Furniture Village which launched a challenge to find the piece of furniture that has remained in continuous use by the same family the longest.
"Despite its great age, it is the most comfortable bed in the castle. Sleeping in such a wonderfully historic bed conveys a real feeling of British history," Georgina Berkeley said.
The bed is listed on an inventory taken on September 20 1608 of New Park Lodge, a family property on the Berkeley Castle estate.