Background::Triple-negative breast cancer (TNBC) is a type of highly invasive breast cancer with a poor prognosis. According to new research, long noncoding RNAs (lncRNAs) play a significant role in the progression of cancer. Although the role of lncRNAs in breast cancer has been well reported, few studies have focused on TNBC. This study aimed to explore the biological function and clinical significance of forkhead box C1 promoter upstream transcript (FOXCUT) in triple-negative breast cancer.Methods::Based on a bioinformatic analysis of the cancer genome atlas (TCGA) database, we detected that the lncRNA FOXCUT was overexpressed in TNBC tissues, which was further validated in an external cohort of tissues from the General Surgery Department of the First Affiliated Hospital of Nanjing Medical University. The functions of FOXCUT in proliferation, migration, and invasion were detected in vitro or in vivo. Luciferase assays and RNA immunoprecipitation (RIP) were performed to reveal that FOXCUT acted as a competitive endogenous RNA (ceRNA) for the microRNA miR-24-3p and consequently inhibited the degradation of p38. Results::lncRNA FOXCUT was markedly highly expressed in breast cancer, which was associated with poor prognosis in some cases. Knockdown of FOXCUT significantly inhibited cancer growth and metastasis in vitro or in vivo. Mechanistically, FOXCUT competitively bounded to miR-24-3p to prevent the degradation of p38, which might act as an oncogene in breast cancer. Conclusion::Collectively, this research revealed a novel FOXCUT/miR-24-3p/p38 axis that affected breast cancer progression and suggested that the lncRNA FOXCUT could be a diagnostic marker and therapeutic target for breast cancer.