The NHL's department of player safety announced the suspension Thursday.
Gilbert hit Ritchie during the second period of the Kings' 4-0 loss to the rival Ducks on Tuesday, making contact with Ritchie's head while driving him into the glass. No penalty was given on the play, but Ritchie didn't return to the game, and he didn't play in Anaheim's loss to Pittsburgh on Wednesday.
Gilbert will lose over $23,000 in salary during his suspension.
He would be eligible to return next week when the Kings visit Montreal. The 33-year-old Gilbert spent the past two seasons with the Canadiens before signing with Los Angeles as a free agent four months ago.