During WWII, an Allied commando team is tasked with an urgent mission: to destroy a pair of massive German guns on the Greek island of Navarone that command a sea channel. These guns threaten Allied naval ships, as they attempt to rescue British soldiers stranded on another island, Kheros, trapped by German troops. With time running out, the fleet is unable to proceed with the evacuation, and the survival of the British soldiers hangs in the balance. The guns are ensconced in an almost impenetrable cliffside fortress, making a frontal attack impossible.

The team, composed of experts from various fields, includes a mountaineer, an engineer, a Greek resistance fighter, and a leading British Major. Disguised as Greek fishermen, they must traverse the Aegean Sea, infiltrate occupied territory, and confront the treacherous mountainous terrain of Navarone. Complicating matters further, personal tensions and conflicting motives among team members threaten to unravel the mission from within. Nonetheless, they must forge ahead, relying on their skills, stealth, and each other to navigate German patrols, overcome natural obstacles, and find a way to bring down the guns before the naval fleet arrives and the window for rescue closes.