In a sample of 7.8 million J/ψ decays collected in the Beijing Spectrometer, the process J/ψ→γηc is observed for five different ηc decay channels: K+K-π+π-, π+π-π+π-, K±KS0π∓ (with KS0→π+π-), φφ (with φ→K+K-) and K+K-π0. From these signals, we determine the mass of ηc to be 2976.6±2.9 ±1.3 MeV. Combining this result with a previously reported result from a similar study using ψ(2S)→γηc detected in the same spectrometer gives mηc=2976.3±2.3±1.2 MeV. For the combined samples, we obtain Γηc=11.0±8.1±4.1 MeV. ©2000 The American Physical Society.