Is an octopus considered to be a mammal?

The egg-laying platypus and the echidna, also known as a spiny anteater of Australia, are very ancestrally old mammals. They lay eggs instead of giving live birth. They're still considered mammals because they're warm-blooded, vertebrate animals with fur that make milk for their young. read more

As Paulo Pereira says, octopuses are mollusks. Mammals are fur (or hair) bearing vertebrates which nurse their young. read more

An octopus is an invertebrate animal, which means it has no spine. More specifically, an octopus is a cephalopod, like squid and cuttlefish. They’re some of the smartest invertebrates. read more

Octopuses are not mammals. They are classified as cephalopods, a class of mollusk. Octopuses are invertebrates, meaning that they do not have a backbone; on the other hand, mammals are vertebrates. read more