Agenda 21 adalah suatu Pelan Tindakan Global untuk Pembangunan Lestari Ke Arah Abad 21. Ia dihasilkan melalui perisytiharan Persidangan Sedunia di Rio de Janeiro, Brazil pada 1992 dihadiri oleh 178 negara termasuk Malaysia. Pelantindakan Global ini mengandungi 40 bab yang mentakrifkan langkah-langkah yang perlu diambil ke arah pembangunan lestari.
Agenda 21 is a Global Action Plan for Sustainable Development Towards the 21st Century. It is produced by the declaration of the World Conference in Rio de Janeiro, Brazil in 1992 which was attended by 178 countries including Malaysia. Global Action Plan contains 40 chapters that describe the steps that need to be taken towards sustainable development.