Political commentator John McGuirk is suing entrepreneur Paddy Cosgrave, a co-founder of the Web Summit, over alleged defamation in a number of posts on Twitter.
Mr McGuirk, who is editor of the conservative Gript website, alleges that tweets posted by Mr Cosgrave last December defamed him.
He alleges the tweets meant that he, Mr McGuirk, had made racist references to former US president Barack Obama.
The proceedings were lodged last week by Mr McGuirk, represented by Robinson Solicitors, in the High Court.
Mr Cosgrave did not respond to a request for comment.
