Fergus McFadden has been banned for Leinster's Champions Cup final against Saracens on 11 May.
The winger has been ruled out for the rest of the season after being handed a six-week suspension.
McFadden, 32, was found guilty of a headbutt on Ulster's Sean Reidy during Leinster's Pro14 defeat in Belfast.
The ban, which accounts for meaningful games, runs until midnight Sunday, 25 August and also rules the player out of two of Ireland's pre-World Cup matches.
McFadden won the last of his 34 Ireland caps during the 2018 Six Nations win against France and will now miss Ireland opening World Cup warm up matches against Italy and England.
Ireland head coach Joe Schmidt will select a 45-man pre-World Cup squad in August and will reduce his panel to 38 players after the match against England at Twickenham before finalising his tournament squad in between the matches against Wales on 31 August and 7 September.
Number eight Reidy went off for a head injury assessment shortly after the first-half incident. He did not return and is a doubt for Ulster's Pro14 quarter-final against Connacht.
McFadden attended a disciplinary hearing via video conference on Thursday after he was cited for an infringement of Law 9.12 - a player must not physically abuse anyone - striking with the head.
McFadden, scored a try in the defeat in Belfast, missed last season's Champions Cup final because of a hamstring injury.