A joint statement issued by the nations said they rejected "destabilising" actions in the disputed waters that threaten regional peace.
The announcement on Sunday commemorated a July 12, 2016, arbitration ruling by a tribunal established in The Hague under the United Nations Convention on the Law of the Sea, saying the landmark decision is "a significant milestone and is final, legally binding and definitive".
China refused to join the arbitration initiated by the Philippines in 2013 after a tense standoff in the contested waters a year earlier that ended with Beijing effectively seizing a disputed shoal.
Beijing rejected the 2016 ruling and continues to defend its claims to virtually the entire sea passage, a key global trade route that has long been feared as one of Asia's most active flashpoints.
"We reaffirm the Arbitral Tribunal's decision that there is no legal basis for China's expansive maritime claims in the South China Sea, including those based on 'historic rights'," the statement said.
The arbitration tribunal largely decided in favour of the Philippines, ruling that under the UN Convention on the Law of the Sea, "there was no legal basis for China to claim historic rights to resources" in the South China Sea outside of its regular territorial areas recognised under the convention.
The convention, largely regarded as the treaty governing the world's oceans and seas, took effect in 1994 and has been ratified by more than 170 countries and parties, including China and the Philippines.
In addition to the US, Britain and Australia, the other countries listed in Sunday's statement included the Philippines, Japan, New Zealand, Canada, Germany, Italy, Estonia, Latvia, Lithuania, Romania and Slovenia.
"We reiterate our strong opposition to any destabilising or unilateral actions including by force or coercion that threaten peace and stability in the region," they said.
Chinese coast guard ships and support vessels have used powerful water cannons, military-grade lasers and dangerous blocking manoeuvres against Philippine forces and fishermen from rival claimant countries that have led to collisions in the high seas and high-risk encounters in the air.
China did not immediately respond on Sunday, but in a statement issued recently through its embassy in Manila, Beijing said it would never recognise the 2016 ruling that it called "illegal, null and void".
"The award will not alter the historical and factual basis for China's sovereignty over the islands of the South China Sea and their adjacent waters," the Chinese embassy in Manila said, adding the ruling "will not weaken China's resolve and determination to safeguard its sovereignty and maritime rights and interests".
