Friends of the oldest museum in Gwynedd fear it faces closure due to a cut in council funding.
The museum was taken over by Gwynedd council in 1991
Supporters of Gwynedd Museum and Art Gallery in Bangor claim the plan to withdraw funding came out of the blue.
Gwynedd council said it faced a significant financial deterioration and it had no option but to review funding. A working group is to consider all options.
The museum was first opened in 1884 by Bangor university.
But it has been run by Gwynedd county council since 1991.
"We were shocked, there was no rumour or hint that this was going to happen, it just fell from the sky on us," said Alan Dyer, chaitman of Friends of Gwynedd Museum and Gallery.
Mr Dyer said he was "as happy as I could reasonably be" that a working group had been set up to consider all possibilities.
The museum's most valuable collection is its archaeological artefacts.
"A collection like this cannot be seen anywhere else in north Wales," he said.
Many people did not realise what was in the city centre museum he said, even though "we try hard to publicise it".
"It is all very accessible, there are no unmade bed artworks here," he added.
John Marjoram, developments officer for Wales with the Museums Association, said Gwynedd council should continue to support the facility.
"If Gwynedd council is serious about history, culture, and the Welsh language then it needs to support Gwynedd Museum," he said.
"Once it is lost you can't get it back as the collections will be dispersed."
Rhys Wyn Parri, head of Gwynedd Council lifelong learning service said it contributed £83,500 to the annual running costs.
But he said since the agreement to run the museum had been made, the financial situation facing the council had "deteriorated significantly".
The museum has free entry and is opened every afternoon from Tuesday to Saturday.