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League of Legends error

"Unexpected error with the login session": a stuck League client

League clientLogin

The message

There was an unexpected error with the login session. Please try again.

What it means

Another copy of the League client is usually stuck running in the background, and the new login trips over it.

What to try first

Sign out of the client, then end every RiotClientServices.exe and League process in Task Manager before logging in again.

Is it you or Riot? If lots of players are hitting this at once, it's probably the servers. Check League server status before you start reinstalling things.

Why the login session breaks

Riot's error table gives the reason in one line, and its dedicated article (updated May 31, 2026) builds the fix around it: a second League client is stuck running where you can't see it. When you log in again, the new session collides with the leftover one.

Don't confuse it with the plain unexpected login error. That one, per Riot, comes down to a shaky internet connection, and it gets a router reset and a DNS change instead.

How to fix it

  1. With the League client in front, press Alt+F4. When it asks, pick Sign out. Riot is specific about that choice, so don't hit Exit.
  2. Open Task Manager with Ctrl+Shift+Esc. End every copy of RiotClientServices.exe and every League of Legends process you find (Riot's article calls it LeagueofLegends.exe). Check the whole list, because there can be several.
  3. Start the League client (or the Riot Client) again and log in.

If the error comes back, Riot says to run through the same three steps again and this time also end KillerServiceNetwork.exe if it's there. That's part of the software on Killer network cards, which Riot says can give your streams bandwidth ahead of League and knock you offline. Riot's Killer guide covers switching it off for good.

Other wordings of the same error

  • Unexpected error with login session
  • Unexpected error with the login session
  • League login session error

Source: Riot Games Player Support, Unexpected Error With Login Session - How to Fix, updated May 31, 2026. Riot's steps are paraphrased here, not copied; checked September 25, 2026.