Triple-negative breast cancer (TNBC) is an operational term that refers to a heterogeneous collection of breast cancers lacking expression of estrogen receptor (ER), progesterone receptor, and HER2. These tumors account for 12-17 % of all breast cancers, preferentially affect young women, are more frequent in women of African and Hispanic descent, and are enriched in the population of patients diagnosed with "interval cancers." TNBCs account for the majority of breast cancers arising in BRCA1 germline mutation carriers (approximately 80%), and approximately 11-16% of all TNBCs harbor BRCA1 or BRCA2 germline mutations. Well-known risk factors for ER-positive cancers, such as reproductive history and hormonal factors, do not appear to have the same correlations for TNBC, and histologic risk factors for TNBC have not been identified. Patients with TNBC have a higher risk of both local and distant recurrence, but this is not mitigated by bigger surgery, and standard criteria should be used to select the approach to local therapy in these patients. Although platinum drugs have shown promise in the treatment of TNBC, standard chemotherapy remains the standard of care outside of a clinical trial.