Lyon ended the eighth round of the French league season with an decisive home victory as Karl Toko Ekambi struck twice for the second week in a row.
"Toko Ekambi played a huge match," said Lyon manager Rudi Garcia. "Let's hope he keeps it up."
Memphis Depay opened the scoring after a pass from Houssem Aouar in the 12th minute.
Toko Ekambi converted a cross from Tino Kadewere at the second attempt in the 34th minute.
In the 41st minute, the Cameroon striker won a penalty that Aouar converted. Three minutes later, Toko Ekambi took advantage of a misunderstanding in the Monegasque defence to score.
"We led 4-0 at half-time on our four shots on target," Garcia said. "In the first half, Anthony Lopes made at least two great saves that allowed us to reach the break in the lead."
Monaco had dominated possession and their coach Niko Kovac agreed that the half-time score flattered Lyon.
"It was a pretty incredible first half," Kovac said. "I have never experienced such a first half before."
Last week in Strasbourg, Lyon led by three goals after 42 minutes only to finish the game clinging to a 3-2 victory.
Wissam Ben Yedder converted a Monaco penalty early in the second half but even though the visitor dominated possession, it could not make the game close.
"We had opportunities to put in a fifth goal but the main thing is to hold on to a good win," Lopes said.
Lyon moved up to sixth and next week face Lille, which is second on goal difference after drawing at Nice.
Lille remains unbeaten after eight matches but trails reigning champion Paris Saint-Germain on goal difference.
Patrick Vieira's Nice sits fifth, four points off the top two.
Kasper Dolberg put Nice ahead less than five minutes into the second half, getting in front of Lille defender Domagoj Bradaric before dinking the ball into the net to score his third goal of the season.
Lille levelled in the 58th minute as Luiz Araujo's pass freed Burak Yilmaz, who hammered home a fierce volley.
The veteran Turkish striker has netted four Ligue 1 goals since signing from Besiktas in the off-season.
PSG had moved to the top of the table with a 4-0 home victory over Dijon.