Brandon Haunstrup has left Pompey to sign for Scottish Premiership side Kilmarnock.
The 23-year-old defender was out of contract with the Blues and turned down the offer of a new deal.
He will now link up with former Fratton team-mate Nicke Kabamba at the Rugby Park outfit, who finished eighth in the top-flight last term.
Haunstrup made 57 appearances after progressing through the Pompey ranks, scoring his only goal in an FA Cup victory at Harrogate Town.
Portsmouth Football Club would like to thank Brandon for his service at Fratton Park and wish him well for the next stage of his career.