4 Dec, 10:19
Grand Slam winners Fiona Coghlan and Nora Stapelton have returned the Women's RBS 6 Nations trophy to Chief Executive John Feehan at the Six Nations offices in Dublin.
Ulster's second Southern Hemisphere signing in two months - following the tying-up of a deal with Waikato scrum-half Isaac Boss - Harrison turns 31 next month, and has played more than 80 Super 12 matches for the ACT Brumbies and the Waratahs.
He made a telling Wallaby debut on the 2001 British and Irish Lions tour, clashing with England's Austin Healy, who famously dubbed the 6ft 8in Sydney-born second row 'a plank'.
With the Super 12 season just two matches in, and the Waratahs currently top, Australian Rugby Union (ARU) Managing Director and CEO Gary Flowers admitted: "Australian Rugby made Justin a very good offer - for a player of his experience and standing in the game - and he was well aware that we were prepared to continue the negotiation process.
"Justin was given the opportunity to continue his career in Australia, but in the end he has decided to head overseas and play for Ulster. It was his decision and we wish him well."
Australia coach Eddie Jones added: "Justin has been a member of the Wallaby squad for four years now and has made an outstanding contribution to the team.
"His departure is disappointing. However, we are confident there are a number of good young players ready to take up the challenge."
Harrison - who did not starting playing the game until leaving school - earned his 34th Test cap for Australia in their 21-19 Twickenham win over England last November.