Bradshaw - who won three Connacht titles with the Tribesmen since making his debut in 2007 - was the longest serving member of the current panel, having also acted as vice-captain to manager Alan Mulholland in 2013.
The Moycullen clubman came off the bench in their 2020 Connacht quarter final defeat to Mayo, and says he has spent the last couple of months considering his future.
"After taking the time to consider my future since the end of the 2020 inter-county season, I have now decided to retire from playing football for Galway.
"It’s been an absolute privilege to represent the county's flagship football team for 14 years, an honour which I never took for granted.
"To Padraic Joyce, I would like to thank you for the opportunity and support that you gave me over the last 12 months in what was an unprecedented year in 2020 and I wish you and the team the very best going forward.
"Furthermore, I would also like to thank all the previous managers whom I played under who entrusted me with the Galway jersey," he said.
Galway boss Padraic Joyce paid tribute to the defender, whom he was a teammate of when Bradshaw emerged on the scene in 2007.
"He is an outstanding footballer and he played every game with real passion and drive. He always gave everything for his club Moycullen and Galway Football.
"He sacrificed all he could in getting his body fit for the challenges year in year out. Having managed him last year I could still see that he was working harder than ever to help Galway Football.
"He always put the team first. We will miss his presence and personality from the Galway set up.
"On behalf of all involved with the Galway Senior Football team I would like to thank Gareth Bradshaw for his commitment and dedication to Galway Football throughout his career and wish him well with Moycullen defending their county title in the coming season," Joyce added.