The discovery of high-temperature superconductivity in pressurized bulk La3Ni2O7 has ignited substantial interest in nickelate superconductors. Unlike cuprates, for which superconductivity predominantly originates from the \(3{d}_{{x}^{2}-{y}^{2}}\) orbital, nickelates exhibit further complexity that arises from contributions from the \(3{d}_{{z}^{2}}\) orbital. This prompts fundamental questions about the pairing mechanism. Despite recent progress in stabilizing superconductivity in La3Ni2O7 thin films at ambient pressure, direct observation of the opening of the superconducting gap has not been achieved. Here we show evidence of the superconducting gap in this material using in situ angle-resolved photoemission spectroscopy. Fermi surface mapping shows two pockets that have slightly larger filling than that reported for non-superconducting single crystals. These bands exhibit moderate electron correlations, characterized by a band renormalization factor of 3–4. Both bands exhibit shifts of the leading edge across the superconducting transition and a gap with a magnitude of approximately 1–2 meV at Fermi momenta along the Brillouin zone diagonal and slightly away from the zone diagonal. This deviates from the conventional \({d}_{{x}^{2}-{y}^{2}}\) gap structure. Additionally, the Ni- \(3{d}_{{z}^{2}}\) -derived band lies approximately 75 meV below the Fermi level, deeper in energy than in non-superconducting single crystals, which indicates that the Fermi surface is dominated by the \(3{d}_{{x}^{2}-{y}^{2}}\) orbital.
