League of Legends’ ranked season system started on July 13, 2010 with Season 1. The game itself launched earlier, in October 2009 , but the first ranked season began the following year.

Quick Scoop

  • Game release: October 2009.
  • First ranked season: July 13, 2010.
  • Season 1 end: August 23, 2011.

Context

Riot used a yearly season structure for many years, then later changed the format into multiple splits in newer ranked years. That means older discussions about “when seasons started” usually refer to the original ranked Season 1 in 2010.

Timeline

Milestone| Date
---|---
League of Legends release| October 2009 10
Season 1 start| July 13, 2010 7
Season 1 end| August 23, 2011 7

If you want, I can also list every LoL season start date in order.