A Freedom of Information request by Scottish Labour showed librarian numbers have plummeted by 32 per cent since 2015.
There were 306.21 full-time equivalent librarians in 2015, but this fell to just 208.71 in 2021.
Figures were not provided by Angus, Edinburgh or Argyll and Bute.
It comes amid warnings next year's local government settlement will have a "detrimental impact" on essential services.
Cosla, the body that represents Scotland' s councils, warned local authorities face a real-terms cut in core funding of £371 million.
Scotland on Sunday, The Scotsman’s sister paper, is running a campaign to support libraries.
Labour MSP Mark Griffin said: “Libraries are at the heart of Scotland’s communities, but they have been decimated under the SNP.
“Time and time again the SNP insist there is no problem, but funding has been slashed and staff numbers have plummeted on their watch.
“Libraries are an essential gateway to information for people of all ages, but these cuts will hit children and families in poverty particularly hard.
“As we fight to close the attainment gap and recover from the chaos the pandemic inflicted on education, libraries will be more important than ever, but they are hanging by a thread with many still closed.”
SNP culture minister Jenny Gilruth said: "Local authorities have a statutory duty to ensure that there is adequate provision of library services for their residents.
"Despite the pandemic exerting unprecedented pressures on our budget, the 2021/22 local government finance settlement of £11.7 billion includes an additional £375.6m, or 3.5 per cent, for day-to-day revenue spending.
“In addition, the value of our overall Covid-19 support package for councils now totals more than £1.5bn.
“Furthermore, the Scottish Government’s £1.25m Public Library Covid Relief Fund, announced in November 2021, is now supporting 23 projects around the country to re-connect communities with their libraries.
“There is a need, however, to ensure our library sector fully recovers from the pandemic. Local authorities have a key role to play here.
"I met with Cosla to discuss the provision of cultural services earlier this month and I look forward to working with their culture conveners group as we take this vital work forward."