This is a list of notable events relating to the environment in 1973. They relate to environmental law, conservation, environmentalism and environmental issues.

• Several thousand pounds of polybrominated biphenyls were accidentally mixed with livestock feed that was distributed to farms in Michigan, because the plant also produced a feed precursor ingredient, magnesium oxide, which was sold to the feed manufacturer.^[1] Adverse reproductive-system effects continued 40 years later to be found in the grandchildren of those who consumed tainted farm products.^[2]

• The snail darter controversy delayed the construction of the Tellico Dam on the Little Tennessee River in the United States when the snail darter fish was discovered in the river.

• The International Agreement on the Conservation of Polar Bears was signed in Oslo, Norway.

• The Endangered Species Act was signed into law in the United States by President Richard Nixon.^[3]

• Human impact on the environment
• List of environmental issues