First Minister Nicola Sturgeon will make her case for Holyrood to be granted the power to stage a second independence referendum in the aftermath of Britain's Brexit vote.
The SNP leader will call on MSPs to back her request to Westminster for a Section 30 order, allowing for a legally-binding vote to be held.
It comes just over a week after she announced plans to hold another referendum on Scotland's future some time between autumn 2018 and spring 2019.
Scottish Conservatives, Labour and Liberal Democrat politicians have already made clear they will seek to block such a ballot.
But the pro-independence Scottish Greens, who have six MSPs, will give the First Minister the support she needs for her motion to be passed on Wednesday afternoon.
Prime Minister Theresa May has already said ''now is not the time'' for another referendum and has indicated the UK Government would reject the SNP's preferred timetable.
Ms Sturgeon's motion calls on the Scottish Parliament to acknowledge ''the sovereign right of the Scottish people to determine the form of government best-suited to their needs'' and ''mandate the Scottish Government to take forward discussions with the UK Government'' on the details of a section 30 order.
The details of the order should ensure that Holyrood can legislate for a vote ''at a time, and with a question and franchise, determined by the Scottish Parliament, which would most appropriately be between the autumn of next year, 2018, when there is clarity over the outcome of the Brexit negotiations and around the point at which the UK leaves the EU in spring 2019'', the motion adds.
In her speech to the SNP conference on Saturday, the First Minister stressed that if the motion is passed, the call for a Section 30 order would become the will of the Scottish Parliament.
She insisted: ''The will of our parliament must and will prevail.''
Ms Sturgeon added on Monday it would be "democratically indefensible" for the Prime Minister to continue to block a referendum if the motion is passed.
Scottish Conservative leader Ruth Davidson insisted a second vote on independence would be the "'wrong course of action to take'', arguing the "'clear majority of Scots say they don't want to go through the uncertainty of another referendum at this time''.
The debate comes as a new poll put Mrs May's approval rating at six percentage points higher than that of Ms Sturgeon.
Sky News surveyed more than 2,000 people with addresses registered in Scotland about whether they believe various party leaders are doing a good or a bad job.
Some 48% of those quizzed said they believe the Prime Minister is doing a good job, while 42% said the same of Scotland's First Minister.
Ms Davidson topped the results table, with an approval rating of 53%, five percentage points above the Prime Minister.
Labour leader Jeremy Corbyn fared worst in the online study, with 16% backing his leadership and 77% describing it as "bad". Kezia Dugdale, Labour's head in Scotland, netted an approval rating of 36%.