Britton joined Swansea from West Ham in 2002, initially on loan, and apart from a six-month spell with Sheffield United in the 2010/11 season he has been with the Welsh club ever since.
The 35-year-old has played 536 games for the Swans and could make his final appearance in the last Premier League match of the season at home to Stoke on Sunday.
“I have decided that this year will be my last as a Swans player,” Britton told the official club website.
“Calling it a day makes this a strange day for me. football is all I have known and, when I was a kid, playing football was all I wanted to do. I have been very fortunate to be able to play professionally for as long as I have.
“It is going to be strange for me, especially when the team come back for pre-season in July.”
Britton was part of the Swansea side which avoided relegation from the football League on the final day of the 2002/03 season.
He was then an integral part of the Welsh club’s climb through the divisions and helped them into the Premier League in 2011.
Britton won the League Cup in 2013 as Swansea claimed the first major trophy in their history, and was part of the following season’s Europa League adventure.
“I have to look back and say I have been very fortunate to have had the career I’ve had,” said Britton, who is to become a club ambassador.
Britton has made 536 appearances for Swansea so far.
“To play as long as I have done and to have been on the journey I have with Swansea has been a privilege.”
News of Britton’s retirement comes the day after it was announced that long-serving Spanish defender Angel Rangel would be leaving Swansea after 11 years.
Rangel, also 35, played 373 games for Swansea after joining from Spanish club Terrassa in 2007 and was appointed club captain in November after Britton was promoted to the coaching staff.
Swansea are almost certain to be relegated this weekend after a seven-season stay in the Premier League.
To stay up they must beat Stoke and Southampton have to lose to Manchester City, while enjoying a 10-goal turnaround in the process.
