The Environment and Sustainable Development Unit of the Organisation of Eastern Caribbean States (OECS-ESDU) is the entity within the OECS Secretariat that is responsible for the provision of natural resource and environmental management services to the member states of the OECS.

The mandate of the OECS-ESDU is to:

Assist Member States in all matters pertaining to the sustainable use of natural resources to ensure the sustainability of livelihoods of the peoples of the OECS.

The mission of the OECS-ESDU is:

"To be a dynamic facilitator for effective management of natural resources for sustainable development in the OECS sub-region through collaboration with and among member states".

The ESDU was formerly known as the NRMU - Natural Resources Management Unit.