Ospreys winger, and Wales international says he has 'so many fantastic memories.'
Despite his best efforts to return to playing for the Ospreys following back surgery early in 2017, he has been unable to make a complete recovery to allow himself to get back to his previous level of performance.
In consultation with specialists, he has made the decision that he has no option but to retire from professional rugby.
Speaking about his decision, Walker said: "It is extremely difficult thing to do, acknowledging and making the decision that you have to retire from the game but it is absolutely the right thing for me to do. I've worked hard to try to get back to where I was pre-surgery but, unfortunately, I recognise that I am not going to be able to do so.
"I'm thankful for the support I've had from my family and from the Ospreys during what has been a tough period for me personally. I'm immensely proud of everything I've achieved on the rugby pitch, be that playing for Swansea, representing my home region, the Ospreys, or gaining my full Wales cap and without the support of my mother, in particular, I wouldn't have able to achieve anything like I have in my career.
"There are so many fantastic memories that will live with me forever and the sport has allowed me to meet some fantastic people who are now firm friends, and experience some great places. I consider myself fortunate.
"The supporters at the Ospreys have always been great for me and now I'm one of you. Although I'll no longer be playing for the team I'll always be an Osprey, whatever my next step is."
The 25-year old came through the ranks of the regional development pathway after starting out at Gorseinon RFC, and played age-grade rugby for the Eyasses before making his senior debut as an 18-year old, coming off the bench in a Liberty Stadium win over Aironi in September 2010.
He featured nine times in the PRO12 during the 2011/12 title winning season and in total made 81 appearances for the Ospreys, scoring 23 tries. He also played 29 times for Swansea, scoring 13 tries.
Capped by Wales across all the age-grades and named in several senior Wales squads, his one cap came against Ireland in August 2015. His last appearance for the Ospreys was in a 31-7 win against the Blues at Cardiff Arms Park at the end of 2016.
Andrew Millward, Managing Director at the Ospreys, paid tribute to Eli, saying:
"Everyone is saddened by this news. Eli is someone who came through the development system and was identified at a young age as having the potential to become a senior player for the region and for Wales with his physical attributes and rugby ability marking him out as someone with a bright future.
"He established a reputation as a quality finisher of the highest level and enjoyed many standout moments in an Ospreys shirt, his try in the unforgettable win over Toulouse at the Liberty Stadium summing up his ability.
"It is a real shame for Eli, and for the Ospreys, that injury has cut short his career before even reaching what should be his prime. However, he should be proud of what he has done in the black shirt and how he has represented himself, his family and the region. Always a fans favourite, he has given us all some special moments to remember and will always be thought of as a true Osprey."