Six out of ten Scots say they would be prepared to pay more in tax if the cash raised went on improving public services or tackling inequality.
Research by polling company Survation found 60% said they would "personally be willing to pay more tax" - with only 15% opposed.
The research, carried out for campaigning organisation 38 Degrees, was released a week before finance secretary Derek Mackay will reveal his Budget plans for next year to the Scottish Parliament.
There is widespread speculation Mr Mackay will raise taxes for better-off Scots, using powers Holyrood has over income tax rates and bands.
Survation's research showed 61% are in favour of proposals which could raise £200m by raising taxes on higher earners while cutting the amount paid by lower-income Scots.
More than 16,000 people have signed a petition from 38 Degrees calling for such a change.
Gordon Maloney, a campaigner with the group in Scotland, said: "These results show the public have come down on the side of bold tax reform to help fund Scotland's public services.
"With the vast majority backing tax rises for better treatment in our hospitals, education for our children and a more equal society - and almost two in three Scots willing to personally pay more - the government has a mandate to be bold.
"MSPs can either be ambitious on tax reform and receive the public's backing - or they can kowtow to the interests of the very richest."
A Scottish Government spokeswoman said: "The serious economic threat posed by Brexit, coupled with continuing UK Government austerity following the UK Government's budget earlier this week, means we are seeing increasing pressure on our public services, and the time is right for a discussion about how we protect these vital services.
"That is why we have started a conversation, including the publication of our discussion paper, to look at how best to use our income tax powers, with the principles of fairness and protecting those on the lowest incomes at the heart of our considerations.
"Following this careful and detailed discussion, we will publish a balanced package of tax and spending proposals as part of the draft budget on December 14."