Objective: To explore the expression and clinical significance of histone deacetylase 5 (HDAC5) in oral squamous cell carcinoma (OSCC) and provide a research basis for targeted therapy of HDAC5. Methods: Screening sample data of OSCC patients in TCGA database, and receiver operating characteristic (ROC) curve analysis was used to evaluate the prognostic value of HDAC5 in OSCC. Kaplan-Meier analysis was also used to analyze the correlation between HDAC5 and the prognosis of OSCC patients. Further, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were used to explore the potential role of HDAC5 in OSCC. Finally, the study was approved by the ethics committee and the expression level of HDAC5 in OSCC was detected by immunohistochemistry (IHC), while the relationship between HDAC5 and the clinical pathological characteristics of OSCC patients was analyzed. Results: The expression of HDAC5 can be used to assess the prognosis of OSCC patients (AUC=0.743). High expression of HDAC5 was significantly correlated with low survival probability in OSCC patients (P < 0.05). OSCC patients with high HDAC5 expression in G3/G4 pathological grading (P=0.022), OSCC patients with high HDAC5 expression in the T3/T4 stage (P=0.028), and OSCC patients with high HDAC5 expression in lymph node metastasis (P=0.019) had lower survival probability. GO and KEGG enrichment analyses showed that genes differentially expressed with HDAC5 were mainly enriched in axon generation, neuronal cell body formation, collagen fiber synthesis, neuroactive ligand receptor interactions, gated channel activity, and extracellular matrix (ECM)-receptor interaction pathways (P < 0.05). The IHC results showed that HDAC5 was highly expressed in OSCC (P < 0.05). The high expression group of HDAC5 had higher T staging (P=0.041) and lymph node metastasis (P=0.010). Conclusion HDAC5 is highly expressed in OSCC and can predict the prognosis of OSCC, and HDAC5 could serve as a therapeutic target for OSCC.