O'Brien's forearm clearly made contact with the face of All Blacks winger Waisake Naholo as the Irish loose forward joined a tackle in the 59th minute of the match at Wellington Regional Stadium.
Naholo was taken from the pitch for a concussion test, which he failed, forcing his replacement. Referee Jerome Garces, who had sin-binned Lions prop Mako Vunipola only minutes before, took no action on the pitch.
"The citing Commissioner ... has cited O’Brien under law 10.4 (a) for allegedly striking All Blacks winger Waisake Naholo with a swinging arm," read a New Zealand Rugby statement.
"The Citing Commissioner said the incident, in the 19th minute of the second half, is deemed to have met the threshold for a red card."
O'Brien has played both tests for the Lions on this tour and losing him for next Saturday's match at Eden Park would be a setback for Warren Gatland's side.
All Blacks centre Sonny Bill Williams will face a judicial hearing later on Sunday after he was shown a red card for a shoulder charge on Anthony Watson in the 25th minute of the match.
(Reporting by Nick Mulvenney; Editing by Peter Rutherford)
