It's thought a levy would reduce the amount of single use plastic that ends up in the sea.
Plaid Cymru wants to see us paying more for non-reusable and non-reyclable plastic items in Wales.
The party believes a levy on disposable plastics could reduce the amount that ends up in the sea and in landfill.
The Welsh Government will be making a statement on devolved taxes in the Senedd later.
Shadow Cabinet Secretary for Energy, Climate Change and Rural Affairs Simon Thomas said: "Plaid Cymru believes in introducing a levy on non-reusable and non-recyclable plastics.
"In April the Welsh Government has the ability to vary and raise taxes.
"I'm confident the best option is to have a polluter pays principle when it comes to taxation and introduce a plastic levy.
"Wales could lead the way with a levy on disposable single-use plastics.
"The carrier bag levy showed how a small policy can make a big difference.
"The recently passed Welsh budget will help to further increase recycling rates through a feasibility study of a deposit-return scheme for Wales.
"A Deposit Return Scheme for glass and cans along with a single use plastic levy, could have a huge impact on the amount of waste generated in Wales.
"Ensuring we have a deposit return scheme for Wales would be another important step in our journey to create a zero waste nation by 2030."