Arc21 is an umbrella waste management group in Northern Ireland representing 6 councils on the eastern coast. It was established in 2003 and formally incorporated in 2004 following a process of increasing co-operation amongst its constituent councils.

Arc21 works on behalf of its partner councils to guide, support and help them deliver their statutory waste management obligations, drive forward innovative waste management programmes, including developing infrastructure, and address greater circularity of resources.

Arc21's six partner councils are Antrim and Newtownabbey Borough Council, Belfast City Council, Ards and North Down Borough Council, Lisburn & Castlereagh City Council, Mid and East Antrim Borough Council and Newry, Mourne and Down District Council.

Arc21 operates within the framework of a legally binding collaborative agreement between all of its councils.