Today's Game 3 between Jin Air Green Wings and SK Telecom has just surpassed the 2014 LNL Winter Qualifers (precedessor of LMS) between ahq e-Sports Club and Hong Kong Attitude as longest game in competitive League of Legends history. The old record was 1 hour, 31 minutes, 21 seconds.
Source of previous longest game
Edit: The new World Record officially is set at 94:38 or 94:39.
Edit 2: Gamepedia lists the new WR as 94:40
