Porites astreoides, commonly known as mustard hill coral or yellow porites, is a colonial species of stony coral in the family Poritidae. It is a common species in the Caribbean Sea and western tropical Atlantic Ocean in North, Central, and South America; and the eastern tropical Atlantic Ocean in western Africa.

Description When it grows in fast-flowing, shallow water, Porites astreoides is encrusting but in calmer water at medium depths it is a massive coral with a smooth, mounded, semi-spherical form and can grow to 60 centimetres (24 in) in diameter. At greater depths it is usually plate-like and in caves and under overhangs the plates are angled to receive the maximum amount of light. It is the only species within the genus Porites not to have a finger-like form. The corallites are small and tightly-packed and give the coral a porous appearance. The polyps each have six tentacles and are generally retracted during the day. This coral is yellow, yellowish-green, pale grey or pale brown, a colour given to it by the dinoflagellate zooxanthellae, microscopic algae that live symbiotically within the coral's tissue.

Porites astreoides is found growing in shallow water on reefs in the Caribbean Sea and in the western-central and southwestern Atlantic Ocean in the Caribbean region and tropical North America, Central America, and South America; and the eastern-central Atlantic Ocean in tropical western Africa. It is a common species on all parts of a reef and in lagoons.