The fifth season of the American ABC fantasy-drama series Once Upon a Time was ordered on May 7, 2015. Like the previous two seasons, it was also split into two volumes, with the first airing from September 27 to December 6, 2015, and the second from March 6 to May 15, 2016. The season also saw the series reach its 100th episode, which aired on March 6, 2016 as the mid-season premiere. Wikipedia