A common chimpanzee has 48 chromosomes. That is 24 pairs in its diploid cells, including one pair of sex chromosomes.
The number is especially interesting because humans have 46 chromosomes, or 23 pairs, despite sharing a recent common ancestor with chimpanzees. Human chromosome 2 formed when two ancestral ape chromosomes fused end to end; in chimpanzees, the corresponding genetic material remains on two separate chromosomes.
Chromosome count does not measure intelligence, complexity, or evolutionary advancement. It simply describes how an organism packages its DNA. Chimpanzees and bonobos both have 48 chromosomes, as do gorillas and orangutans, while humans are unusual among living great apes in having 46.
A common mix-up is confusing chromosome pairs with individual chromosomes: 24 pairs means 48 chromosomes, not 24.