The long-serving midfielder has spent his entire club-career in San Sebastian, racking up 530 appearances since making his first-team debut back in October 2003.
Indeed, the 34-year-old is fifth on Sociedad's all-time appearance list and he has continued to be a regular this season, featuring 24 times in La Liga to date.
Sociedad are certainly grateful for the years of service they have received from Prieto and they have been quick to pay tribute to the former Spain under-21 international following the confirmation of his retirement plan.
"His class on and off the field will remain forever etched in the memory of the Real Sociedad family," read a statement from the Basque club. "Thanks for everything, Xabi!"
Prieto, who has also scored 80 goals during his career with Sociedad, could make his last appearance for the club when they take on Barcelona at the Camp Nou on the final day of the La Liga season.