As the science of transformation of matter, chemistry provides knowledge, innovation and practice that are fundamental to the current efforts to achieve sustainability in the face of challenges that include multiple environmental crises (including pollution, climate change and biodiversity loss) and looming shortages of ‘critical’ materials. This article presents the case for chemistry and the chemical sciences adopting material stewardship as a central mission, whose aim is to transform and use the Earth's available stock of material resources in ways consistent with ensuring sustainability for people and for the physical and biological systems of the planet on which all life depends. The implications of this mission are examined, including for chemistry's contributions to extending knowledge, processes and products required for stewarding the Earth's physical and biological materials and systems. The mission includes supporting energy transitions necessary to stabilise Earth systems that are increasingly perturbed by anthropogenic effects. An overview is presented of how chemistry's mission of material stewardship interconnects with sustainability frameworks providing broad principles and goals, including the UN's Sustainable Development Goals and the Planetary Boundaries and Human Security frameworks, as well as with specific chemistry movements and orientations (including green, sustainable, circular and one-world chemistry) and enabling tools (e.g. systems thinking, material circularity and life cycle assessment) that provide guiding concepts, pathways and capacities for chemistry's contributions towards sustainability. The utility of the material stewardship mission is exemplified through three case studies, related to a product type, a sustainability tool, and a sustainability movement. The need is emphasised for the chemistry profession to work across disciplines to help shape policy and practice towards a sustainable future. This includes engaging with others in the processes of negotiation that shape global agreements on goals, policies and programmes that impact on sustainability. Critical ones currently in progress include the efforts to find mechanisms to reduce greenhouse gas emissions to limit global warming to the UN's target of not more than 1.5 °C above pre-industrial levels by 2050, and to establish a UN Science-Policy Panel on chemicals.