PARIS — President François Hollande of France on Monday awarded the Legion of Honor, France’s highest award, to three Americans and a Briton for their role in stopping a gunman on a high-speed train traveling to Paris from Amsterdam on Friday.

The three Americans — Airman First Class Spencer Stone, 23; Alek Skarlatos, 22, a specialist in the Oregon National Guard; and their friend Anthony Sadler, 23 — received the honor in the gilded halls of the Élysée Palace, where they were joined by Chris Norman, 62, a British consultant.

“One need only know that Ayoub El Khazzani was in possession of 300 rounds of ammunition and firearms to understand what we narrowly avoided, a tragedy, a massacre,” Mr. Hollande said at the ceremony, referring to the suspect in the attack, a Moroccan who is in police custody and denies that he had planned to stage a terrorist attack.

“Your heroism must be an example for many and a source of inspiration,” Mr. Hollande added. “Faced with the evil of terrorism, there is a good, that of humanity. You are the incarnation of that.”