The 57-year-old made a stridently left-wing speech speech to around 25,000 of the party faithful turned out at Le Bourget near Paris on Sunday.
Hollande hammered home his attachment to French secular and socialist values, saying that the world of finance was his real enemy.
"My real adversary has no name, no face, no party, it will never be a candidate, even though it governs... it's the world of finance," Hollande said.
He blasted this world "which has seized control of the economy, of society and even our lives," adding that it had breached "all rules."
"I will be the president who ended privileges," he added.
"I am aware of my task: embodying change, getting the left to win and renewing faith in France," Hollande said to rapturous applause at the start of the 90-minute speech.
Hollande's campaign slogan "Change Is Now" was emblazoned on a patriotically blue, white and red stage.
Britain's newspapers honed in on the presidential frontrunner's attack on the world of finance, but also his appearance.
In a country where Prime Minister David Cameron refused to sign up to a new EU treaty last month because he wanted to protect the interests of Britain's financial sector, Hollande's attacks on bankers did not go unnoticed.
At the Le Bourget rally, Hollande was "shaking his fists, drenched in sweat, permatanned and svelte after the most famous crash diet in French politics", the centre-left Guardian newspaper said.
Hollande had taken aim at the world of finance and blamed it for creating a country with extremes of rich and poor, it added.
The Financial Times said Hollande described the banking industry as a "faceless ruler" who sought to make an impression on the wider French public by attacking "some carefully chosen national betes noires".
"These included globalisation, unemployment and shrinking domestic industry. But uppermost were bankers," the business paper said.
Hollande's speech was preceded by a mini-concert by former tennis champion turned pop star Yannick Noah, who consistently polls as one of France's most popular celebrities.
The bespectacled Hollande has a reputation as a manager rather than as a charismatic leader, and Sunday's rally was an opportunity to show his flair as an impassioned orator.
French paper L'Humanité on Monday hailed "a speech from the left, far from the tepid social-liberal waters of five years ago."
Outlining his priorities as education, health, justice and tax reforms, Hollande said he would propose a new pact with European powerhouse Germany in January next year, if elected.
While he still leads the right-wing President Nicolas Sarkozy in opinion polls, that lead is slowly being eroded by resurgent far-right and centrist parties, but also by his own perceived dithering.
Recalling his conservative family roots in Normandy, Hollande thanked his parents for having given him the freedom to choose Socialism.
He lashed out at those who have criticised him for never having served as a minister, and sought to portray himself as the natural heir to the last successful Socialist presidential candidate, François Mitterrand.
"Some people criticise me for never having been minister. When I see who they are today, I'm reassured!" he said, recalling that a campaigning Mitterrand was criticised in 1981 for having been minister too many times.
Former International Monetary Fund chief Dominique Strauss-Kahn had been favourite for the Socialist party nomination before he was arrested on sexual assault charges in New York in May.
The charges were dropped, but his presidential ambitions were ruined.
The Socialists have criticised Sarkozy for not yet having declared his own candidacy while nevertheless reserving the right for officials from his ruling UMP party to snipe at opponents' campaign promises as they tread water.
Hollande has consistently led opinion polls with 28-30 percent of votes predicted in the first round on April 22nd, ahead of President Sarkozy's 23-24 percent.
Polls say that far-right leader Marine Le Pen would garner 18-20 percent of votes and centrist candidate François Bayrou 12-14 percent: but their numbers are on the rise, at the expense of both Sarkozy and Hollande.
Hollande's detailed campaign manifesto is to be unveiled on Thursday.