Wallabies legend George Smith has officially announced his rugby retirement after nearly two decades at the top of the sport.

Smith has been playing with UK side Bristol this season but was released by the club after a short-term contract, a decision that left his future open-ended.

The 38-year-old confirmed his retirement in a statement on Monday evening, reflecting on a journey through rugby that has crossed many borders.

"Finally the day has come where I officially announce my retirement from professional rugby," he wrote.

"It's been an absolute privilege to play professionally for the past 20 years. Rugby has provided and given me so much. The dreams that I had of playing rugby professionally as a young bloke, I'm fortunate to say that I've lived them and experienced so much more during my time."

Smith singled out former Brumbies and Wallabies coach Eddie Jones in his statement, thanking the now England mentor for his support from day one of his professional rugby life.

"Special mention to Eddie Jones, who has been a constant supporter and mentor of mine throughout this time," he wrote.

"The day I rocked up to sign my first Brumbies contract with dreadlocked hair, board shorts and thongs. I think back and shake my head as to why he didn't just turn me away tight there and then.

"I'm grateful for his advice and friendship."

Smith has been a constant in the rugby landscape since making his Super Rugby debut back in 2000 for the Brumbies, also playing for French sides Toulon, Lyon and Stade Francais; Japanese side Suntory, English sides Wasps and Bristol and the Reds in his most recent Aussie stint.

Smith also tallied 111 caps for the Wallabies in a glittering career, the reputation of which still lives on strongly in Australia.

The flanker was the first John Eales Medallist back in 2002 and won the medal again in 2008.

"The day my father registered me with the Warringah Roos at 4 years of age in manly I found myself returning to the game every year thereafter," he wrote.

"I was extremely lucky in my career to have landed myself in Canberra as a young 19-year-old kid, having the luxury of being tutored by the finest peers and coaches in the game at the ACT Brumbies.

"I had a great time there and look back fondly. Those early years in Canberra shaped a part of my rugby identity and further encouraged my personal ambitions to better myself as a rugby player.

"I'm also proud of the opportunities I had to represent the Wallabies on numerous occasions in the past. On reflection, the time spent earning those caps were well worth it."

"Looking back I'm pleased with the impression that i leave behind on my playing contributoin and it is time now to start looking forward to the next chapter that awaits my family and I."

Smith didn't give any hints as to what the next step would be for he, wife Louisa and their children Wyatt, Soleil, Ryker and Lafaele, but he would be very much in demand in the coaching realm.

He spent time in the England camp in 2016, helping as a breakdown consultant, and was also involved in the Wallabies fold in the 2017 June Series.