Cats can eat basil, and it is not considered poisonous or toxic to them. Basil is safe for cats to consume in small amounts, but it offers no significant nutritional benefit since cats are obligate carnivores and primarily need meat in their diet. While most cats do not find basil appealing, if a cat does eat it, it generally won't harm them. However, eating large quantities might cause digestive upset like vomiting or diarrhea for some cats. Also, basil essential oil should be avoided as it can be harmful to cats. Overall, basil can be given as an occasional treat but is not necessary or especially beneficial for cats.