Literacy and numeracy are central to lifelong learning and sustainable development. In today's fast-changing world, both skills are essential to achieving independence and wellbeing, and provide the basis for sustainable societies with constant socio-economic progress. "Literacy and Numeracy from a Lifelong Learning Perspective," a new policy brief by the UNESCO Institute for Lifelong Learning (UIL), challenges the assumption that literacy and numeracy are stand-alone skills to be learned within a set timeframe. It argues instead for a lifelong learning perspective: investing in sustained learning and updating already acquired skills. The brief shows that for literacy and numeracy to be effective, they must be seen as a continuum of proficiency levels and not as a simple dichotomy between who is 'literate' and who is 'illiterate'. The policy brief provides a set of recommendations to support policymakers in addressing youth and adult literacy and numeracy by adopting holistic, multi-sectoral approaches within a lifelong learning perspective. This underpins the importance of encouraging a culture of learning at different levels -- family, community and society -- to address the manifold demands of lifelong learners. The paper also points out various ways that governments can implement literacy and numeracy programmes. Optimal implementation of literacy programmes will not only help countries meet the 10 targets of Sustainable Development Goal (SGD) 4, which calls for 'inclusive and equitable quality education and promote lifelong learning opportunities for all', but the other 16 SDGS, as well.