Eugenie Le Sommer's 11th goal in her last 11 appearances for France in all competitions gave the tournament hosts an early lead in Paris.
Before half-time a pair of towering Renard headers made it 3-0 to Corinne Diacre's side, who are among the favourites to win the tournament, allowing them to ease off after the interval.
But with six minutes to go France wrapped things up in superb style, Amandine Henry scoring from outside the penalty area to send a strong message to their World Cup rivals.
France opened the scoring in just the ninth minute at a packed Parc des Princes.
A composed attack led to Henry squaring a low cross for Le Sommer to steer a first-time finish past helpless Korea goalkeeper Kim Minjung.
France seemed to have doubled their lead in stunning fashion in the 26th minute, Griedge Mbock Bathy swivelling to volley home a headed pass from Renard, but the goal was ruled out for offside following a VAR check.
More goals duly arrived before the break as Gaetane Thiney's corner was powered home by Renard before the defender's aerial power told again, this time from Amel Majri's set piece.
Korea's comparative lack of physicality continued to give France a major advantage but Henry's effort from the edge of the penalty area was easily gathered by goalkeeper Kim.
Substitute Kang Chaerim went close to scoring a spectacular consolation for Korea, with their first shot in the 69th minute, but her rising drive narrowly cleared the France crossbar.
France got sloppy in the closing stages and a rare Renard mistake allowed Lee Mina to run through on Sarah Bouhaddi's goal, but composure deserted the forward and she fired wide of the target.
But Les Bleues were able to sign off the tournament opener with a fourth goal in the 84th minute, Henry whipping a sensational strike across Kim from 25 yards out.
Key Opta Facts
- France's 4-0 win over Korea Republic in this match was the biggest win by a host nation in their opening game of a FIFA Women’s World Cup tournament since China PR defeated Norway 0-4 in 1991. In that year, Norway went on to reach the final before losing to the United States.
- France's victory means that seven of the eight host nations of a FIFA Women’s World Cup have won their opening game of that tournament, including the last six in a row. The only host nation not to win their opening match at a Women's World Cup tournament was Sweden in 1995 (0-1 vs Brazil).
- Le Sommer's goal was her 75th for France in all competitions; the only female with more is Marinette Pichon (81 goals).
- Ten of Renard's last 11 goals for France have come from headers and this was her first international goal since March 2017 vs England.
- Renard scored twice in an international match for France for the first time since November 2013 vs Bulgaria – 2017 days ago.