AbstractIn this study, it is found that the lncRNA, DNA damage inducible transcript 4 antisense RNA1 (DDIT4‐AS1), is highly expressed in triple‐negative breast cancer (TNBC) cell lines and tissues due to H3K27 acetylation in the promoter region, and promotes the proliferation, migration, and invasion of TNBC cells via activating autophagy. Mechanistically, it is shown that DDIT4‐AS1 induces autophagy by stabilizing DDIT4 mRNA via recruiting the RNA binding protein AUF1 and promoting the interaction between DDIT4 mRNA and AUF1, thereby inhibiting mTOR signaling pathway. Furthermore, silencing of DDIT4‐AS1 enhances the sensitivity of TNBC cells to chemotherapeutic agents such as paclitaxel both in vitro and in vivo. Using a self‐activatable siRNA/drug core–shell nanoparticle system, which effectively deliver both DDIT4‐AS1 siRNA and paclitaxel to the tumor‐bearing mice, a significantly enhanced antitumor activity is achieved. Importantly, the codelivery nanoparticles exert a stronger antitumor effect on breast cancer patient‐derived organoids. These findings indicate that lncRNA DDIT4‐AS1‐mediated activation of autophagy promotes progression and chemoresistance of TNBC, and targeting of DDIT4‐AS1 may be exploited as a new therapeutic approach to enhancing the efficacy of chemotherapy against TNBC.