"Peace is secured only through strength and its strength on both sides of the Atlantic, fortified by readiness, shared military capabilities and an unwavering political will," Hegseth said at the US war cemetery in Collville-sur-Mer.
"Our world is safer and more prosperous when the United States of America and our allies are strong, free and unapologetic in defence of our Western tradition of freedom."
Hegseth said "America will lead" but insisted that "capable allies must be right there with us, shoulder to shoulder in the breach when it matters".
"We stand by our allies, and we expect our allies capable and ready to stand alongside us," he added.
The politician - dubbed the secretary of war by US President Donald Trump - argued that "much of the West" has grown "comfortable" since World War II.
"We forgot that freedom is not free. We forgot that peace is not wished into being. It is bought with purpose, with honour and with strength," he said.
"The men who landed on these beaches knew this."
Hegseth appeared to make a comparison between the Normandy landings in Nazi-occupied France - which began on June 6, 1944 and played a key role in the defeat of Adolf Hitler's Third Reich - and migrant crossings in the Mediterranean, which he labelled an "invasion".
"Sadly, today, different European beaches are stormed by different dangerous ideologies," he said.
"Beaches in Spain and Italy and Greece and Bulgaria. Boats and men arrive," he said.
"When will European capitals do something about that invasion? Or is it too late?" he added.
"I pray not, and I believe not."
Hegseth was accompanied by his French counterpart, Catherine Vautrin, at the commemoration on Saturday.
with AP
