Nicola Sturgeon will demand a second Scottish independence referendum to take place next year.
The Scottish First Minister told SNP Conference her party was laying the groundwork for such a referendum, and would have the legal basis in place by the end of 2019.
She told party faithful in Aberdeen: "For Scotland, Brexit shows that the Westminster system is broken and it is broken utterly beyond repair.
"Conference, we have a cast iron mandate for an independence referendum. That fact is beyond doubt.
"But we don't just have a right to offer the people of Scotland a choice over their future. In the circumstances Scotland now faces, we have a duty to do so and that is what we intend to do."
She went on: "But let me be clear about this. The process by which we choose Scotland's future must be capable of actually achieving independence. It must allow majority support to be expressed clearly and unambiguously. It must be legal and it must have the recognition of the international community.
"Why? Because our job is not just to deliver a referendum. Conference, our job is to deliver independence.
"And my call is that the referendum must happen next year. And we are getting ready."
Delegates took to their feet in a lengthy standing ovation at the announcement.
The First Minister will try to trigger a second referendum with something called a 'Section 30 order'.
This is a power under Section 30 of the 1998 Scotland Act.
It lets "the Queen in Council" take something the Scottish parliament doesn't currently control, and give the Scottish parliament control over it.
Ms Sturgeon went on to say an independent Scotland, as part of the European Union, would have a "unique advantage" which could make it a "magnet for global investment".
With a general election "imminent" Ms Sturgeon said her party would fight that campaign with a "clear, simple and unambiguous" message.
That will be: "Vote SNP to demand independence and secure Scotland's right to choose."
Ms Sturgeon said: "Some polls suggest that an election might result in a hung parliament.
"The SNP will never put the Tories into power.
"But I have a message for any Westminster party that wants SNP support.
"If you don't respect Scotland's right to choose our own future at a time of our own choosing, don't even bother picking up the phone."
The first Scottish referendum, on 18 September 2014, rejected independence by 55% to 45%.