Chronic infection with hepatitis C virus (HCV) is an important cause of end stage liver disease worldwide. In the United States, most HCV-related disease is associated with genotype 1 infection, which remains difficult to treat. Drug and vaccine development was hampered by inability to culture patient isolates representing HCV genotypes 1-7 and subtypes; only a recombinant 2a genome (strain JFH1) spontaneously replicated in vitro. Recently, we identified three mutations F1464L/A1672S/D2979G (LSG) in the nonstructural (NS) proteins, essential for development of full-length HCV 2a (J6) and 2b (J8) culture systems in Huh7.5 cells. Here, we developed a highly efficient genotype 1a (strain TN) full-length culture system. We initially found that the LSG substitutions conferred viability to an intergenotypic recombinant composed of TN 5' untranslated region (5'UTR)-NS5A and JFH1 NS5B-3'UTR; recovered viruses acquired two adaptive mutations located in NS3 and NS4B. Introduction of these changes into a replication-deficient TN full-length genome, harboring LSG, permitted efficient HCV production. Additional identified NS4B and NS5B mutations fully adapted the TN full-length virus. Thus, a TN genome with 8 changes (designated TN cell-culture derived, TNcc) replicated efficiently and released infectious particles of ∼5 log(10) focus-forming units per mL; passaged TNcc did not require additional changes. IFN-α and directly acting antivirals targeting the HCV protease, NS5A, and NS5B, each inhibited full-length TN infection dose-dependently. Given the unique importance of genotype 1 for pathogenesis, this infectious 1a culture system represents an important advance in HCV research. The approach used and the mutations identified might permit culture development for other HCV isolates, thus facilitating vaccine development and personalized treatment.