The Sunday Herald has become the first newspaper publicly to back a "Yes" vote in the Scottish independence referendum.
The front page of the weekly title states "Sunday Herald says Yes" and is decorated with a giant thistle and saltires in a design by artist and "Yes" supporter Alasdair Gray.
The paper supported the SNP in the 2007 and 2011 Scottish Parliament elections.
It said it would remain balanced in its reporting.
An article on the newspaper's website said: "The Herald & Times Group, publisher of the Sunday Herald, The Herald and the Evening Times, is giving the titles' editors freedom to take their own editorial position on the constitution.
"The company is non-political and neutral.
"The Herald has not declared an opinion on the referendum question. It will be up to its editor to decide when and if to do so."
A spokesman for the pro-Union Better Together said: "This is not exactly a surprise. Anybody who has read the Sunday Herald since the campaign started would know that they favour breaking up the UK.
"Newspapers are perfectly entitled to back one side or the other, and we would expect a number of Scottish newspapers to support Scotland remaining in the UK."
Blair Jenkins, Yes Scotland chief executive, said: 'The Sunday Herald is the first national newspaper to endorse either side in the debate about our country's future and we are delighted that it has chosen to support Yes.
"The Sunday Herald's editorial is passionate, inspiring and, above all, a statement of common sense and irresistible logic."
The Sunday Herald sold an average of 23,907 copies each week in the second half of 2013, according to the latest circulation figures from the industry-owned Audit Bureau of Circulation (ABC).
It claims to have a significant growing online readership, with 1.6m reading the Herald website monthly.