YBX1 promotes esophageal squamous cell carcinoma (ESCC) progression by stabilizing SMOX mRNA through m5C-dependent mechanisms. The study reveals that YBX1 is frequently upregulated in ESCC tissues compared to matched non-tumor tissues. Functional assays show that YBX1 enhances ESCC cell proliferation and metastasis in vitro and in vivo. Mechanistically, YBX1 binds to SMOX mRNA, which contains an m5C modification in its coding sequence. NSUN2, an RNA methyltransferase, facilitates this m5C modification, and YBX1 stabilizes SMOX mRNA by recognizing the m5C modification. This stabilization activates the mTORC1 signaling pathway, promoting ESCC progression. The study highlights the role of YBX1 in ESCC development through m5C-dependent regulation of SMOX mRNA, suggesting YBX1 as a potential therapeutic target for ESCC. YBX1 expression is associated with poor patient survival in ESCC. NSUN2 is also upregulated in ESCC and contributes to tumor progression by modulating m5C levels. The YBX1/m5C-SMOX axis is critical for ESCC progression, with SMOX expression positively correlated with YBX1 and NSUN2. The findings suggest that targeting this axis could be a promising therapeutic strategy for ESCC.YBX1 promotes esophageal squamous cell carcinoma (ESCC) progression by stabilizing SMOX mRNA through m5C-dependent mechanisms. The study reveals that YBX1 is frequently upregulated in ESCC tissues compared to matched non-tumor tissues. Functional assays show that YBX1 enhances ESCC cell proliferation and metastasis in vitro and in vivo. Mechanistically, YBX1 binds to SMOX mRNA, which contains an m5C modification in its coding sequence. NSUN2, an RNA methyltransferase, facilitates this m5C modification, and YBX1 stabilizes SMOX mRNA by recognizing the m5C modification. This stabilization activates the mTORC1 signaling pathway, promoting ESCC progression. The study highlights the role of YBX1 in ESCC development through m5C-dependent regulation of SMOX mRNA, suggesting YBX1 as a potential therapeutic target for ESCC. YBX1 expression is associated with poor patient survival in ESCC. NSUN2 is also upregulated in ESCC and contributes to tumor progression by modulating m5C levels. The YBX1/m5C-SMOX axis is critical for ESCC progression, with SMOX expression positively correlated with YBX1 and NSUN2. The findings suggest that targeting this axis could be a promising therapeutic strategy for ESCC.