Democratic Gov. Janet Mills signed the bill into law Tuesday.
The Natural Resources Council of Maine says Maine’s the first state to enact such a ban. Similar legislation passed Maryland’s legislature in April, but it’s unclear whether that state’s Republican governor will sign it.
Supporters say the law will reduce litter in lakes, rivers and coastal waters. It takes effect in 2021.
Mills called it an “important step forward in protecting our environment.” She said it creates consistency for businesses while providing time to adjust.
The law prohibits “covered establishments” like restaurants and grocery stores from using polystyrene containers. Hospitals, seafood shippers and stores selling pre-packaged meat are exempt.