Le Pen, 48, the presidential runner-up to centrist Emmanuel Macron, will represent her northern fiefdom of Henin- Beaumont, a depressed former mining town, the National Front's Steeve Briois said.
After easily making it into the run-off in the northern town of Henin-Beaumont against 12 rivals in the first round, Le Pen went on to beat a political novice from new president Emmanuel Macron's La Republique en Marche (REM) party, Anne Roquet.
"We are the only force of resistance to the watering down of France, of its social model and its identity," she said defiantly." Le Pen said. "We will express this defence in our own way in the National Assembly.
Le Pen picked up almost 59 percent of the vote giving her a convincing victory over REM's Roquet.
But her anti-EU, anti-immigration FN failed to capitalise on the populist wave that helped propel Donald Trump to the US presidency and spurred Britain's vote to leave the European Union.
Le Pen's party won 8 seats in the 577-seat National Assembly, dashing her one-time hopes of emerging as the main opposition to Macron's centrist Republic on the Move (REM) party.
But after qualifying for the second round of the presidential election back in April pollsters had predicted her National Front (FN) party could win as many as 50 seats in the National Assembly.
The National Front party leader, handsomely beaten by Macron in the second round of the presidential election once again blasted France's electoral system and demanded proportional representation, that would give her party many more seats in parliament.
"Its a scandal that our party that picked 7.6 million votes in the first round of the presidential election and three million more in the second round, cannot form a group in the French parliament," said Le Pen.
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A group can be formed if a party has 15 seats, which would grant it more access to finances, office space and meeting rooms.
Plus parliamentary groups are granted more speaking time when it comes to government questions as well as a role in setting the parliamentary and influential committee positions.
To rub salt into the wounds of National Front (FN) chiefs, France's other anti-system party, the leftist France Insoumise (France unbowed) won enough seats to form a vital group.
The FN had two lawmakers in the outgoing parliament, one of whom Marion Marechal Le Pen, will not return.
The other was Gilbert Collard, who will return after narrowly winning his seat in the Gard department of southern France.
But Collard accepted it wasn't a good night for his party.
"The National Front has taken a hell of a blow to the head," he said.
The FN leader is currently a lawmaker in the European Parliament but was clear about her hopes of winning a legislative seat in France for the first time.
Soon after losing out to France's new president Emmanuel Macron in the presidential elections, Le Pen announced that she would be running for a parliamentary seat because it was crucial that there were lawmakers ready to oppose Macron's policies.
Le Pen's partner and party deputy Louis Aliot announced he had won his seat in south western France.
But there was also disappointment for senior FN figure Florian Philippot, the architect of the FN's policies to scrap the euro common currency, who lost in the former industrial area of Moselle in eastern France.
Le Pen and the FN have benefitted from a confluence of factors including the 2015 migrant crisis and the string of jihadist attacks that have hit France.
The party has a particular populist appeal in France's northern rustbelt, which is dotted with shut-down factories and mines.
In the presidential vote, Le Pen aimed to capitalise on the same rejection of traditional politics that swept Donald Trump to the White House and sparked Britain's vote to leave the EU.
She was roundly criticised for a poor performance in a brutal TV debate with Macron days before the presidential runoff that potentially cost her votes.
"The National Front has not recovered from the period between the two rounds (of the presidential election) and its successive mess-ups," Brice Teinturier of the Ipsos polling institute said on France 2 TV.
Le Pen fought for the same seat in 2012, losing by 118 votes to the Socialist Philippe Kemel, who was eliminated this year in the first round of the parliamentary election last Sunday.
Le Pen has spent the past six years since taking charge of the FN trying to expunge the xenophobic, anti-Semitic ethos engendered by her father, who co-founded the party in 1972.
Under Marine Le Pen, the FN has consistently improved its electoral scores, notching up records in past regional, European Parliament and presidential elections.