Ko Nom Sao — which translates straightforwardly as "female breast island" — is a pair of small limestone karst islets in the western part of Phang Nga Bay. They are tiny (the larger covers barely a hundred metres across) and uninhabited, but from the right angle their near-identical profiles rising from the water make the name obvious. They are a standard landmark on longtail routes through the bay's northern section.
The islands are typical of the bay's geology: sheer vertical limestone walls rising from the water, undercut at the base by wave erosion, with vegetation clinging to any horizontal surface. They are not a destination in themselves but form part of the backdrop that makes Phang Nga Bay one of the most striking seascapes in the region.