One of Bristol's main cultural attractions is being lost to London.
The trustees will keep the building, but offer it for lease
The British Empire and Commonwealth Museum has announced it is to move in an effort to engage a "larger international audience".
The trustees are in negotiations over where to house the existing archives and accommodate a programme of major exhibitions and events.
The museum is currently housed in a former railway terminus designed and built by Isambard Kingdom Brunel.
Director Dr Gareth Griffiths said: "Relocation to London presents a major opportunity for the museum to widen its reach and engage new audiences with this important and formative part of our shared past.
"We have enjoyed great success over the last five years of operation and are extremely grateful to the people of Bristol and all those who have supported us."
Leader of Bristol City Council Helen Holland said: "We are confident that our new Museum of Bristol, due to open in 2010, will continue to provide the city's tourists and residents with a fascinating insight into Bristol's role as a key player in the British Empire and Commonwealth over the centuries - in both good times and bad."
The trustees said they would retain control of the historic building at Temple Meads to ensure it was appropriately protected and maintained.
It will be offered on the market as a leasehold property.