The triple planetary crisis of climate change, pollution and biodiversity loss represents the single greatest human rights challenge of our era. In July 2022, the UN General Assembly adopted a historic resolution on ‘The human right to a clean, healthy and sustainable environment’ (A/Res./76/300). The resolution “recognises that sustainable development, in its three dimensions (social, economic and environmental), and the protection of the environment, including ecosystems, contribute to and promote human well-being and the full enjoyment of all human rights, for present and future generations.” Land and Environmental Human Rights Defenders (EHRDs) play a vital role as levers of change in protecting the environment and standing up for communities and individuals who are disproportionately impacted by en vironmental harm. For years, they have been at the front line as advocates for sustainable practices and rights-based development, and in holding duty bearers and businesses responsible for unsustainable practices and violations of all peoples’ right to a clean, healthy and sustainable environment. At the same time, EHRDs continue to be vulnerable to human rights violations as they face growing resistance to their vital work to support a just and sustainable future for people and the planet. Violations against EHRDs are observed in different forms including criminalisation, harassment, threats, and killings. Analysis by Front Line Defenders found that in 2021, 358 human rights defenders were killed, more than half of which (59%) worked on land, environmental, and indigenous rights. By failing to provide adequate support and enabling frameworks to protect and bolster the work of EHRDs, there are many missed opportunities to accelerate achievement of the Sustainable Development Goals, advance environmental rule of law and increase compliance with in ternational environmental commitments. However, the challenges and obstacles faced by EHRDs, as well as their important contributions to the attainment of environmental goals including Agenda 2030, are increasingly being recognised across all regions. There are also strengthened efforts to continue to support their work and improve the conditions in which EHRDs work. This toolkit will provide a set of resources to enable EHRDs to protect, promote and realise the right to a healthy environment and support their important role to tackle the planetary crisis and reach Agenda 2030. This knowledge toolkit aims to provide a practical reference for EHRDs to support their work in promoting environmental rights and to prevent and mitigate security issues.