ObjectiveTo explore the potential causal relationship between 91 inflammatory factors and the risk of lung cancer (LC). MethodsBy extracting related data of inflammatory factors and LC and its subtypes from public databases of genome-wide association studies (GWAS), bidirectional, repeated, multivariable Mendelian randomization (MR) and subgroup MR methods were used for analysis. The inverse variance weighted method was mainly used for causal inference, and a series of sensitivity analyses were applied to verify the strength of the results. ResultsHigher levels of CD5, interleukin-18 (IL-18), and oncostatin-M (OSM) were causally associated with a lower risk of LC, while nerve growth factor-β (NGF-β) and S100 calcium-binding protein A12 (S100A12) were associated with an increased risk of LC. Subgroup MR analysis results showed that IL-18 had a causal relationship with a reduced risk of lung adenocarcinoma, while NGF-β and S100A12 had a causal relationship with an increased risk of lung adenocarcinoma; CD5 and OSM had a causal relationship with a reduced risk of lung squamous cell carcinoma; NGF-β had a causal relationship with an increased risk of small cell lung cancer. ConclusionFive inflammatory factors, including CD5, IL-18, OSM, NGF-β, and S100A12 have a causal correlation with the risk of LC, providing potential targets for early screening of LC patients and development of therapeutic drugs.