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Glueballs are a firm prediction of QCD, candidates had been proposed but no firm conclusions had been reached until recently. In a coupled-channel analysis of the S-wave amplitude from BESIII data on radiative J/ψ decays and further data, ten scalar isoscalar resonances were required to fit the data. Five of them were interpreted as mainly-singlet, five as mainly-octet resonances in SU(3). The yield of scalar resonances showed a striking peak, called G0(1865), with properties expected from a scalar glueball. It is produced abundantly in radiative J/ψ decays above a very low background, and the decay analysis of the scalar isoscalar mesons requires a small glueball content in the flavor wave function of several scalar resonances. The glueball content as a function of the mass shows a peak compatible with the peak in the yield of scalar isoscalar mesons. The sum of the fractional glueball contributions is compatible with one. The peak has all properties expected from the scalar glueball. At the end, first evidence for the tensor glueball is discussed.