Snowball Earth
There were three or four significant ice ages during the late Neoproterozoic. Of these, the Marinoan was the most significant, and the Sturtian glaciations were also truly widespread. These were both in the Cryogenian period, before the Ediacaran. The million year long Gaskiers glaciation did not lead to global glaciation, although it was probably as intense as the late Ordovician glaciation. The status of the Kaigas glaciation or "cooling event" is unclear. Some do not recognise it as glacial, and others believe it may indeed be a third ice age. It was certainly less significant than the Sturtian or Marinoan glaciations, and probably not global in extent. Evidence does  suggest that the Earth underwent a number of glaciations during the Neoproterozoic.