Prime Minister Shinzo Abe is expected to speak at a ceremony in Itoman, at the southern tip of the island, near to the spot where terrified locals jumped or were pushed to their deaths on the orders of Imperial soldiers taught never to surrender.
More than 100,000 Okinawans and 80,000 Japanese troops died in the 82-day battle for the strategically placed island chain.
Over 12,000 American soldiers also perished in what many feared was a foretaste of the fight they would have to wage for the Japanese mainland.
Entire families were wiped out, and almost everyone on the subtropical island lost at least one relative.
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Many committed suicide by plunging off cliffs rather than surrender to the Americans, who found thousands more locals dead in the caves where they had been hiding to escape the furious US bombardment, which came by air, land and sea.
The anniversary comes with feelings running high on Okinawa - a one-time independent kingdom annexed by Japan in the 19th century and now the reluctant host to more than half of the 47,000 US troops still stationed in the country.
However, Tokyo and Washington have both insisted that the plan to move it - conceived two decades ago - is the only viable option for shuttering Futenma Air Station.
Renewed local opposition to the proposal and a series of angry protests have coincided with a push by Abe's nationalist government to give Japan's well-resourced, but tightly restricted, military more leeway to act internationally.
The ceremony in Itoman is scheduled to begin around 10am (0630 IST).