We succeeded in synthesizing a new intermetallic compound with a AuCu3-type structure, LaBi3, by utilizing a high-pressure technique. Reacting Bi and LaBi at 450 degrees C under a pressure of 3.4 GPa resulted in the crystallization of LaBi3 with an a-axis lattice parameter of 4.99 +/- 0.02 angstrom. Sharp superconducting transitions were observed in both its magnetic susceptibility and electrical resistivity at 7.3-7.4 K. The upper critical field mu H-0(c2) (0) and Ginzburg-Landau coherence length xi(0) were estimated to be 1.70 T and 139 angstrom, respectively. The superconducting transition temperature T-c was found to decrease linearly with increasing applied pressure with a slope of -0.26K GPa(-1). Band structure calculations indicated that this compound has a multiband nature and that its Fermi energy is located exactly at one of the peak density of states.