Noxious may refer to:
- Poison, substances that can harm or kill .
- Noxious weed, a plant designated by the government as injurious to public health, agriculture, recreation, wildlife or property
- Noxious stimulus, an actually or potentially tissue damaging event, may be mechanical, chemical or thermal
- Federal Noxious Weed Act of 1974, a United States law that established a federal program to control the spread of noxious weeds