Pompey have signed midfielder Terry Devlin from Glentoran for an undisclosed fee.
The 19-year-old Northern Ireland under-21 international has penned a three-year deal, with the club option of a further 12 months.
Blues boss John Mousinho said: “Terry was one of the outstanding players in the Northern Irish league last season.
“He’s an attacking midfielder who adds qualities to our group that we perhaps don’t already have here.
“Terry can run, he can compete and he can score goals and I’m excited to bring such a talented prospect over to England.
"We do feel that he has a very promising future in the game, but we also believe that he can make an impact for us during the forthcoming season."
“We do feel that he has a very promising future in the game, but we also believe that he can make an impact for us during the forthcoming season.”
Devlin joined Glentoran from Dungannon Swifts last summer and netted five goals in 35 appearances for the club.
He helped them finish third in the Irish Premiership, then win a play-off to qualify for the Europa Conference League.
Devlin his represented his country up to under-21 level, but has also been called up to senior training camps.