Zemmour promised a "reconquest" against decades of decline during his nearly an hour-and-a-half-long speech, the first he has given since declaring his candidacy.
He said he was calling his party "Reconquest," a name that evokes the historic period known as the Reconquista, when Christian forces drove Muslim rulers from the Iberian peninsula.
With echoes of Donald Trump's first campaign for U.S. president, Zemmour promised to slash immigration and taxes to cheers from flag-waving supporters that organizers put at 15,000. A Reuters count put their number at around 10,000.
Zemmour, who has been convicted for inciting racial hatred, is the main challenger to long-time far-right figure Marine Le Pen for a place in a second run-off round of next April's election, most likely against President Emmanuel Macron.