Background: Hepatocellular carcinoma (HCC) is the second lethal malignancy among all cancers. Many molecular alterations have been found in HCC. However, the interactions and modulatory mechanisms among these molecules in HCC are still unclear. Methods: CTB-193M12.5 expression in tissues and cells were detected by quantitative polymerase chain reaction (qPCR). In vitro experiments were conducted to evaluate the function of CTB-193M12.5 in cell proliferation, apoptosis, migration and invasion. The interaction between CTB-193M12.5 and nuclear receptor binding SET domain-containing protein 1 (NSD1) was assessed by RNA??? protein pull-down and RNA immunoprecipitation assays. The roles of CTB-193M12.5 on WNT10B and Wnt/??-catenin signaling was detected by chromatin immunoprecipitation assay, qPCR, Western blot, and dual luciferase reporter assay. Results: We identified a novel prognosis-related long noncoding RNA (lncRNA) CTB-193M12.5 in HCC. CTB-193M12.5 was upregulated in HCC and its high expression was correlated with alpha fetoprotein, large tumor size, aggressive clinical characteristics, and poor survival. Functional experiments showed that CTB-193M12.5 enhanced HCC cellular proliferation, suppressed HCC cellular apoptosis, and promoted HCC cellular migration and invasion. CTB-193M12.5 knockdown exerted opposite effects in HCC. Mechanistic investigation demonstrated that CTB-193M12.5 was mainly distributed in nucleus. Histone methyltransferase NSD1 was identified as a CTB-193M12.5 interactor. CTB-193M12.5 bound and recruited NSD1 to the promoter of WNT10B, leading to an increase in di-methylation of histone H3 at lysine 36 (H3K36me2) and the reduction of tri-methylation of histone H3 at lysine 27 (H3K27me3) at WNT10B promoter. Therefore, CTB-193M12.5 epigenetically activated WNT10B transcription. Through upregulating WNT10B, CTB-193M12.5 further activated Wnt/??-catenin signaling. Functional rescue experiments demonstrated that overexpression of WNT10B reversed the tumor suppressive roles of CTB-193M12.5 knockdown, while Wnt/??-catenin signaling inhibitor ICG-001 abolished the oncogenic roles of CTB-193M12.5 overexpression. Conclusion: CTB-193M12.5 was a highly expressed and poor prognosis-related lncRNA in HCC. CTB-193M12.5 functioned as an oncogenic lncRNA through promoting NSD1-mediated WNT10B/Wnt/??-catenin signaling activation.