Observation of the decay Ds+ ? ??+?

Using 7.33 fb(-1) of e(+)e(-) collision data collected by the BESIII detector at c.m. energies between 4.128 GeV and 4.226 GeV, we observe for the first time the decay D-s(+/-) -> omega pi(+/-)eta with a statistical significance of 7.6 sigma. The measured branching fraction of this decay is (0.54 +/- 0.12 +/- 0.04)%, where the first uncertainty is statistical and the second is systematic.