Eto'o – a three-time Champions League winner among other honours – last played for Qatari outfit Qatar SC in 2018-19.
And the 38-year-old ex-Cameroon striker appears set for life after football following Friday's Instagram post.
"THE END, TOWARDS A NEW CHALLENGE," Eto'o wrote.
"Thank you all big love... adrenaline."
Eto'o enjoyed a trophy-laden career after emerging from Real Madrid's youth team in 1997 – making three appearances for the Spanish giants.
He won the Champions League twice with Barcelona and again during his time at Inter, where Eto'o was part of the club's 2009-10 treble-winning side.
In total, Eto'o celebrated 15 club titles – including three LaLiga trophies – following spells with Mallorca, Barca, Inter, Anzhi Makhachkala, Chelsea, Everton, Sampdoria, Antalyaspor, Konyaspor and Qatar SC.
Eto'o earned 118 caps for Cameroon as he became the country's all-time leading scorer with 56 goals, while winning two African Cup of Nations titles and gold at the 2000 Olympic Games.
Samuel Eto'o is the only man in football history to win back-to-back trebles.— Squawka Football (@Squawka) September 7, 2019
2008-09 x Barcelona
2009-10 x Inter Milan
Just one incredible accolade from a remarkable career. pic.twitter.com/UNXFatd4nC