Pastors from churches throughout the country have signed their names to an open letter calling on First Minister Alex Salmond to protect the institution’s current definition.
The move follows similar calls from Scottish leaders of the Catholic Church.
The letter warns any change to the law would have “significant implications across society” and may lead to other changes to marriage – including the acceptance of polygamy.
It states: “Marriage – although it has been undermined in recent decades – remains a vital universal institution that has benefited Scottish society for centuries.
“The marriage of one man to one woman, for life, for the rearing of children in a stable environment, is a cornerstone of society. It is embedded in history and in cultures around the world.
“Government did not invent marriage, and it is astonishing that it is seeking to legally redefine it at the behest of a small minority.
“What is to stop it being redefined further? There is a very real risk of definition-creep.
“If marriage is redefined, who is to say that, for example, polygamy should not be legalised?”
The churches claim that more than 20,000 parishioners attend their services every week and believe the Government has underestimated how strongly many Christians feel about the issue.
One signatory, Rev David McCarthy, of St Silas Episcopal Church in Glasgow, said: “Changing the definition of marriage would have profound effects on our society, not least for Scotland’s children.
“Traditional marriage gives kids the complementary parenting of a mother and father which same-sex marriage does not.”
Rev Jim Turrent, Lead Pastor of Central Baptist Church, Dundee, added: “If marriage is redefined once, what is to stop it happening again?
“Canada has legalised same-sex marriage, and now there is a legal case in a Canadian court trying to legalise polygamy.
“Mexico City legalised same-sex marriage two years ago, now the city is proposing temporary marriages that only last two years. Once you start to unpick marriage, the whole fabric can unravel.”
The Scottish Government launched a 14-week consultation on same-sex marriage in September this year. This is due to finish on December 9.
At the launch of the consultation, the Government said its view was that gay marriage should be allowed.
However, Deputy First Minister Nicola Sturgeon added that faith groups who did not want to carry out gay marriages should not be made to do so.
Since then the Government has been locked in a dispute with the Catholic Church, which has vehemently opposed the potential change to the law.
Philip Tartaglia, the Bishop of Paisley, warned of a “serious chill in relations” between the two over the proposals.
The bishop, who has argued that same-sex marriage is wrong in principle, said: “Marriage is uniquely the union of a man and a woman, which, by its very nature, is designed for the mutual good of the spouses and to give the children who may be born of that union a father and a mother.
“A same-sex union cannot do that. A same-sex union should not therefore be called marriage.”
His comments were also echoed by the Archbishop of Glasgow Mario Conti who branded same-sex marriages “meaningless”.
A spokesman for the Scottish Government said that no decision has yet been taken adding: “We are continuing to receive responses to the same-sex marriage consultation.”