Poison ivy is a group of three plant species in the genus Toxicodendron, formerly all assumed to be a single species known as T. radicans, in the family Anacardiaceae. These plants are found in North America and East Asia. They are best known for the contact dermatitis caused by physical contact with their leaves, which is brought on by urushiol secreted by the plant. This can cause severe allergic reactions. The three species of poison ivy are:
- Toxicodendron radicans, eastern poison ivy, found in eastern North America and Central America
- Toxicodendron rydbergii, western poison ivy, found in much of North America except the southeast
- Toxicodendron orientale, Asian poison ivy, found in eastern Asia
