Environmental systems are exposed to more simultaneous contaminations than ever from a wide spectrum of sources, such as industrial, agricultural, urban, and household, leading to more complex pollution that poses challenges for ecosystem balance and human health. Traditional monitoring methods, which focus on targeted analysis, are useful for monitoring legacy and priority pollutants, but fall short in comprehending the vast chemical diversity present in the real environmental matrices, which cannot be replicated by standard analytical processes. Non-targeted analysis (NTA) has rapidly emerged as a powerful game-changing tool for learning not only chemicals but also both known and unknown contaminants and also offers the potential to identify thousands of unique chemicals per analysis. The combination of new technologies such as high-resolution mass spectrometry (HRMS), multidimensional chromatographic approaches, and machine learning-assisted data workflows yields a comprehensive understanding of chemical pollution in water, soil, air, sediments, foods, and biological materials. Intermediates like transformation products, metabolites, pharmaceuticals, microplastic additives, emerging contaminants, and per- and polyfluoroalkyl substances (PFAS) are also quantified rather than reporting at their limits of quantification (LOQ). This chapter provides a comprehensive overview of NTA principles, analytic approaches, computational tools, and environmental applications. NTA offers a unique ability to evaluate complex contaminant mixtures and cumulative exposure that approximate real-world conditions. Although key challenges of chemical space, analytical complexity, and data harmonization remain, there are emerging opportunities for previous progress, such as artificial intelligence, open-science platforms, and regulatory frameworks. NTA is situated at the intersection of advanced analytics and environmental risk assessment to provide ways to shift from compliance-driven monitors toward holistic discovery-based pathways critical to protecting ecosystems and public health in the Anthropocene.