Extended gamma-ray sources provide significant information about particle propagation. 4FGL J1626.0–4917 was labeled as an unassociated source in 4FGL catalog without known counterparts at other wavelengths. We report an analysis on 4FGL J1626.0–4917 with 17 yr Fermi Large Area Telescope data and archival Chandra X-ray Observatory data. We find extended GeV emission around this source, which can be modelled by a Gaussian disk of 0°.28 radius with a significance of the extension of 7.2σ. The gamma-ray spectrum of 4FGL J1626.0–4917 has a photon index of 2.73 ± 0.12. The gas content, including molecular, neutral and ionized gas, was investigated and the potential hadronic origin is discussed. The derived gas mass around 4FGL J1626.0–4917 is ∼1.1 × 103M⊙. The diffuse GeV gamma-ray emission may likely originate from the interaction between accelerated protons in 4FGL J1626.0–4917 and the target proton in surrounding gas, although the leptonic process cannot be ruled out. The X-ray spectral analysis was performed, which reveals a point source inside 4FGL J1626.0–4917. We investigate potential counterparts, including the stellar cluster NGC 6134 and the supernova remnant G335.2+0.1. Our results highlight the complexity of unidentified extended gamma-ray sources and the need for further observations.

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