A Wales Under 20s international and former member of Wales Sevens squad, Robinson was called into the Wales senior squad for the training camp in Poland in January 2012 ahead of the Six Nations Championship the same year.
Robinson won three international caps scoring two tries; he scored his first international try in his debut match against Barbarians at the Millennium Stadium.
His debut regional try came in his first competitive appearance against Ulster in September 2014. He played his last game for the Scarlets in December 2015 taking on Glasgow Warriors in the European Rugby Champions Cup at Scotstoun Stadium.
Jon Daniels, Scarlets General Manager of Rugby said; "It is with great sadness that we as a region have to confirm Harry's retirement from rugby. He's a talented young player who had a bright rugby future ahead of him.
"It has been a difficult time for Harry as he has worked exceptionally hard to make a full recovery. I am sure the qualities that got him to the top of the rugby tree in Wales will stand him in good stead in his future career. On behalf of the Board and everyone here at the Scarlets I would like to wish him the very best in the future."
Speaking openly about the decision to retire at only 23 years of age Harry said:
"I never thought I would be in this position at the age of 23 - having to call an end on my professional rugby career at such an early age. I am utterly devastated and it is a very, very bitter pill to have to swallow.
"During a game at the end of last season I suffered a significant neck injury that subsequently needed serious neck surgery. It came as a huge shock to hear the surgeon explain that it was unlikely I would ever return to play professional rugby.
"This was not a prognosis that I wanted to believe or accept. Following successful surgery to ensure that I was at no greater risk of making my injury and condition worse I was determined to come back to play again for the Scarlets. It is difficult to accept that I will never do this again.
"I have worked so hard over the last 10 months to return to full fitness and regain the functionality I had before the injury. It is with great regret that I have been unable to do this. As it has turned out the consultant was correct with his initial assessment of my injury and the ultimate impact on my career.
"Whilst I am devastated I count myself very lucky and enormously privileged. I have had a fantastic six years as a professional rugby player with both Cardiff Blues and Scarlets. I have travelled all over the world at every age grade, Wales 7s and the Welsh squad. I have made many friends who I know will be friends for the rest of my life.
"I would like to thank a whole host of people - the Scarlets; the coaches and the medical team there who have supported me through my recovery with patience and understanding.
"To the Blues and Dai Young who gave me my first professional contract. To all the players I have played with, and against, who have made my playing years such a blast. I walk away with fond memories that will stay with me forever. I wish that it had lasted longer but it was not to be. Sometimes these are the cards you are dealt in life.
"New challenges lie ahead of me now and I will embrace these with the commitment and dedication I have learnt over the years as a player."
