A phosphor comprises a crystal phase with a chemical composition (Lu1-p-q, Cep, Mq)xβyγzO. M denotes one or more elements selected from the group consisting of Y, La, Sc, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb. β contains Si, which constitutes 90% or more by mole of β. γ contains N, which constitutes 90% or more by mole of γ. The variables x, y, z, p, and q satisfy 5.5≤x≤6.5, 10.5≤y≤11.5, 19.5≤z≤20.5, 0