Background <p>Cardiorespiratory fitness (CRF) is a powerful predictor of numerous health outcomes; however, its relationship with liver health remains unclear. This study examined the associations of CRF with non-invasive markers of liver steatosis and fibrosis in a large, health-screening cohort, and explored potential effect modification by demographic, cardiometabolic, and clinical factors.</p> Methods <p>In this independent healthcare-based cross-sectional study of 39,197 UK adults (32% female; mean ± SD, age 45.8 ± 9.0&#xa0;years), CRF was objectively estimated as peak oxygen uptake (ml∙kg⁻¹∙min⁻¹) during submaximal treadmill and cycle ergometer tests. Hepatic steatosis and fibrosis were defined using validated non-invasive indices: Fatty Liver Index (FLI) and Hepatic Steatosis Index (HSI) for steatosis, and Fibrosis-4 Index (FIB-4) and NAFLD Fibrosis Score (NFS) for fibrosis. Multinomial logistic regression examined associations between CRF and low-, intermediate-, and high-risk categories for each index, adjusting for demographic, cardiometabolic, and clinical covariates (excluding component variables of the respective indices).</p> Results <p>For FLI and HSI, each 1&#xa0;ml∙kg⁻¹∙min⁻¹ higher CRF was associated with 3–5% lower odds of intermediate steatosis risk and 8–9% lower odds of high steatosis risk (<i>P</i> &lt; 0.001). For FIB-4 and NFS, higher CRF was associated with 1–3% lower odds of intermediate fibrosis risk and 2–6% lower odds of high fibrosis risk (<i>P</i> ≤ 0.011). Associations were stronger in females and weaker in individuals with less favourable metabolic profiles.</p> Conclusions <p>Higher CRF was associated with lower odds of hepatic steatosis and fibrosis across multiple validated non-invasive indices. These findings highlight CRF as an integrative biomarker of hepatic and cardiometabolic health, and modifiable target for steatotic liver disease prevention and management.</p>