PARIS — President Emmanuel Macron of France won a crucial stamp of approval on Sunday as voters gave him and his allies a decisive majority in parliamentary elections, but a record-low turnout cast a shadow over his victory, pointing to the hurdles he will face as he seeks to revive the country’s economy and confidence.

When the votes were counted, Mr. Macron’s party, La République en Marche (the Republic on the Move) and its allies had won 350 seats in the 577-member National Assembly, the lower house of Parliament.

Mr. Macron, a relative political newcomer who was elected on May 7, had called for a strong mandate to advance his legislative agenda, including plans to loosen France’s restrictive labor laws. Voters swept in many first-time candidates, including some of Arab or African ancestry, and elected more than 200 women, a record in France’s modern history.

For the two mainstream parties, the outcome was a bleak repudiation: The center-right Republicans and their allies were relegated to a distant second place, with an estimated 135 members for its bloc in Parliament, while the Socialists and their allies, who had a majority in the last election, saw their bloc reduced to an estimated 45 seats.