Fillon easily beat Bordeaux Mayor Alain Juppe in the Republican party's first ever US-style primary runoff Sunday, getting about 66% of the vote.
"Victory is mine. It is a substantive victory built on belief," Fillon said as he spoke to supporters after his win. "We have all the assets to be a modern, sovereign nation in the lead in Europe."
Fillon could face far-right National Front Party leader Marine Le Pen
in the final round of the presidential vote next spring, as voters are widely expected to boot out the Socialist Party that has ruled France since 2012 under the leadership of President Francois Hollande, whose popularity is waning.
"This past presidential term has been pathetic," Fillon said in criticizing Hollande. "It is time to end it and start moving forward as we have never done in 30 years. For this we will need everyone."
Fillon, 62, is a lawyer who served as prime minister between 2007 and 2012 under Sarkozy.
He's a social conservative who has talked of ending France's famed 35-hour work week and getting tough with the country's powerful trade unions. He has also spoken of cutting public spending, abolishing the wealth tax, reducing immigration and investing billions in security, defense and justice.
A hard line on immigration has also bolstered Le Pen, whose anti-Europe stance is gaining popularity among French voters. In an interview with CNN last week
, she said she'd been emboldened by Donald Trump's surprise victory in the United States.
"It makes the French realize that what the people want, they can get, if they mobilize themselves," she said.
Fillon's sudden rise
Just a month ago, Fillon was considered an unlikely bet for the presidency, but he won over voters with a polished performance in televised debates.
Polls had him mostly in third place, but he apparently struck a popular tone in the country's fight against Islamic terrorism and ISIS after publishing a new book, "Beating Islamic Totalitarianism."
The first round of the primary, on November 20, put Fillon well ahead, with 44.1% of the vote. Juppe received 28.6% and former President Nicolas Sarkozy came in third with 20.6%, eliminating him from the final round
French newspaper Liberation morphed Fillon's face with Thatcher's in a cover image this week -- no doubt inspired by the Republican's tough talk on unions
and pledge to cut 500,000 jobs from the civil service.
As a Catholic from Le Mans, a city in northwest France, Fillon symbolizes the traditional provincial right.
The father of five lives
with Welsh-born wife Penelope in a 12th-century castle
near where he grew up. Fillon also is a race car enthusiast who once appeared on France's "Top Gear" TV program.
Fillon's main rival, Juppe, is also a former prime minister, under President Jacques Chirac.
He had been seen as a reliable and experienced politician, and a moderate, but was tainted by scandal, including a 2004 prison sentence for corruption.