Circular RNAs (circRNAs) have emerged as crucial regulators of human cancers. Glutaminolysis supplies cancer cells with adequate nitrogen and carbon to replenish the tricarboxylic acid cycle, contributing to the survival and progression of tumor cells. However, the association between circRNAs and glutaminolysis remains unclear. In this study, we showed that circHECTD1 expression was markedly upregulated in gastric cancer (GC) and was associated with lymph node metastasis and American Joint Committee on Cancer stage. The circHECTD1 expression level was found to be an independent prognostic factor for GC patients. circHECTD1 knockdown inhibited GC cell glutaminolysis, proliferation, migration, and invasion, whereas circHECTD1 overexpression promoted GC progression. Dual-luciferase and RNA immunoprecipitation assays demonstrated that miR-1256 was a direct downstream target of circHECTD1. circHECTD1 targeted miR-1256 and subsequently increased the expression level of USP5. The circHECTD1/miR-1256/USP5 axis exerted its tumor-promoting effects by activating the downstream β-catenin/c-Myc signaling pathway. In vivo mouse models further verified the oncogenic roles of circHECTD1 in GC. Our results revealed that circHECTD1 is a glutaminolysis-associated circRNA that promotes GC progression. The circHECTD1/miR-1256/USP5 axis could thus be used as a therapeutic target for GC.