[en] We report the direct measurement of the ⁷Be solar neutrino signal rate performed with the Borexino detector at the Laboratori Nazionali del Gran Sasso. The interaction rate of the 0.862 MeV ⁷Be neutrinos is 49±3_stat±4_syst counts/(day·100 ton). The hypothesis of no oscillation for ⁷Be solar neutrinos is inconsistent with our measurement at the 4σ C.L. Our result is the first direct measurement of the survival probability for solar ν_e in the transition region between matter-enhanced and vacuum-driven oscillations. The measurement improves the experimental determination of the flux of ⁷Be, pp, and CNO solar ν_e, and the limit on the effective neutrino magnetic moment using solar neutrinos