Hayes told his teammates on Tuesday morning about his intentions to call it quits, and admitted he cried when doing so.
The 34-year-old has played 291 games for the Saints since being drafted with pick No. 11 in the 1998 AFL Draft from the Pennant Hills Football Club in New South Wales.
If he plays every game from hereon, the star Saint will finish his stellar career on 297 games.
Six moments that define Lenny Hayes' career
Despite falling shy of achieving the ultimate team success in losing Grand Finals in 2009 and 2010, Hayes has enjoyed a glittering career.
The midfielder's accolades include the 2010 Norm Smith Medal (in the drawn Grand Final), three All Australian guernseys (2003, 2005 and 2009) and three club best and fairest awards (2003, 2010, 2012).
Hayes also captained the Saints in 2004 and 2007.
Having signed a one-year contract extension at the end of last year, Hayes said last month that he had already begun weighing up his playing future.
GALLERY: Lenny Hayes' football life
The expectation was that season number 16 was always going to be his last.
With the Saints going through a rebuilding phase, Hayes has played an important role in mentoring the club's young players this season, but he has continued to contribute on the field, averaging 24.9 disposals from 14 games in 2014.
Lenny Hayes has been a fixture at St Kilda since 1999. Picture: AFL Media
Hayes has been widely respected throughout his career for his fierce attack on the ball and his intense desire to compete.
Click here to check out all of 2014's retirements and delistings