Alex Salmond said the independence referendum in September gives his party "the opportunity of a lifetime".
He was speaking at the start of the SNP spring conference in Aberdeen, where delegates first paid tribute to former SNP MP and MSP Margo MacDonald, who died last week after battling Parkinson's disease.
He said the SNP had had many stars in its history, but "no star has burned more brightly and shone more luminously than Margo MacDonald".
He went on to say that with the vote on independence and the party's 80th anniversary both taking place in 2014, it is a "momentous year".
He told party activists: "The SNP is now 80 years old, but I like to think actually we're 80 years young, 80 years young in particular because we look forward this year to the flowering of our nation, to the fulfilment of the hopes and dreams we've had and carried with us for so long.
"There has been a continuing thread through these 80 years - that this is not an ordinary political party. We're a highly successful political party.
"We're a highly successful political party, but we're not an ordinary political party. We're not an ordinary political party because we are always, and always have been, and in this year above all, we are part of a movement. That movement, that aim, that ambition, is the freedom and independence of our country."
He said there are now 159 days until the independence referendum and "the chance, the opportunity of a lifetime, the opportunity to fulfil, to culminate, the aims and the efforts of the party over these 80 years".
The First Minister said the historic vote gives them "the chance then to take this country forward, to build and achieve the society we know we can be in Scotland, the prosperous, just society".
He added: "What a year, what an opportunity. What fulfilment in this year of 2014."