In Genesis 6:19, Noah is told to bring two of every kind of living creature aboard the Ark, one male and one female. The instruction is part of the preparation for preserving life through the flood.
Genesis 6:20 says the animals will come to Noah, while Genesis 6:21 tells him to collect food for himself and the animals. The wording “of every kind” is a biblical category, not a modern zoological classification such as species, genus, or family.
A related passage creates a common source of confusion. Genesis 7:2–3 gives Noah additional instructions concerning clean animals and birds, describing larger numbers for those categories. Readers therefore encounter both the general pair-based instruction in Genesis 6 and the later distinction involving clean animals.
The answer to this question is specifically the number in Genesis 6:19: two, one male and one female. It should not be expanded into a claim about the exact number of modern biological species on the Ark, because the narrative’s categories and its total animal count are not defined in modern scientific terms.