Yes, although getting multiple winners without enabling Shared Victories in settings is highly improbable. If two empires have the same score when the game ends by time limit they will both be counted as winners. Before version 1.5.0 this was the only known way of having multiple winners. For Shared Victories see mschuett's answer above.
I speculate that if two empires fulfil differing win conditions on the same turn this would also happen, wonder victory for example.
Source: Tie = Victory