Nottingham scrum-half Finlay Barnham has retired after taking medical advice following a six-month spell on the sidelines recovering from concussion.
Barnham, 24, said the decision was taken with "deep regret" after consulting club doctor Abraze Khalique and two specialist neurologists.
"The last six months have been very difficult personally," said Barnham.
"After receiving the same advice from three medical professionals, it became clear I needed to make this decision."
Barnham joined Nottingham in 2010 from the Leicester Tigers academy and has made 83 appearances for the club, scoring one try.
He added: "This sport has been a huge part of my life for as long as I can remember and I consider myself very privileged to have been given the opportunity to ply my trade professionally.
"I've had some fantastic experiences as a rugby player and I wouldn't swap them for anything."
Concussion has become a major talking point in the sport recently.
Long-serving Nottingham winger David Jackson was forced to retire in December 2013 following a head injury and has since campaigned to raise awareness of the issues and help support those who have been affected.