Scottish independence: Sturgeon wants indyref2 by 2021
The first minister told Holyrood that she would introduce legislation soon to set the rules for another vote.
But she will not yet ask the UK government for a Section 30 order, which underpinned the last independence referendum in 2014.
She also challenged her party to grow support and demand for independence.
Ms Sturgeon told MSPs: "A choice between Brexit and a future for Scotland as an independent European nation should be offered in the lifetime of this parliament.
"I can confirm that the Scottish government will act to ensure that the option of giving people a choice on independence later in this term of parliament is progressed."
The next Scottish Parliament election is due to be held in 2021.
Ms Sturgeon said she hoped legislation will be in place by the end of this year, which would allow a vote to be held once a Section 30 order is granted by the UK government.
The UK government has previously said it would not agree to any request for a Section 30, with Downing Street saying on Tuesday that this position had not changed.
But Ms Sturgeon insisted: "If we are successful in further growing the support and the demand for independence, then no UK government will be able to stop the will of the people or stop that will being expressed."
The first minister added: "The immediate opportunity we now have is to help stop Brexit for the whole UK - and we should seize that opportunity. But if that cannot be achieved, dealing with the consequences of Brexit and facing up to its challenges will be unavoidable.
"I believe that the case for independence is stronger than ever. I will make that case, but I know others take a different view.
"So, as we take the necessary legislative steps over the next few months, I will also seek to open up space for us to come together and find areas of agreement as mature politicians should."
But she warned that if the only alternative was a "failed and damaging status quo", then "the process of change will pass them by and support for independence will grow".
Scottish Conservative interim leader Jackson Carlaw said Ms Sturgeon's statement was "inherently divisive".
He added: "Astonishingly, the way Nicola Sturgeon thinks we can come together is for Scotland to be plunged into another divisive referendum within the next 18 months.
"The SNP's plan is clearly to divide families, workplaces and communities all over again, and for the foreseeable future. That is not what the majority of Scotland wants."