The 39-year-old revealed in a social media post that he has made the decision after doctors advised him to have hip replacement surgery.
"The time has become," Aduriz's message began. "Many times, I have said that football will leave you before you leave it.
"Yesterday, the doctors told me to go to see the surgeon, sooner rather than later, to get a prosthetic to replace my hip and to try and go about my everyday life, as normally as possible.
"Unfortunately, my body has said 'enough'. I can't help my team-mates the way I would like to, nor the way that they deserve. That is the life of a professional athlete. Simple, very simple."
Aduriz had intended 2019-20 to be his last season and it seemed he would get the chance of a famous farewell, with Athletic set to face Basque rivals Real Sociedad in the Copa del Rey final.
However, the suspension of the Spanish season due to the coronavirus pandemic means there is no certainty when, or even if, the Copa final will be played.
"Unfortunately, we are living through situations much more grim and painful; the pandemic that we are suffering from has left us with irreparable damage and we have to keep fighting it, together," he said.
"Therefore, I don't want you to worry about me, this is just an anecdote. Let's forget about the finals we dreamt about, because we will have time to say goodbye. And yes, the time has come to say goodbye, and this is how the road ends for me - unforgettable and marvellous, from beginning to end.
"Thank you, from the bottom of my heart."
Aduriz started his senior career with Athletic but also enjoyed spells with Real Valladolid, Real Mallorca and Valencia.
Something of a late bloomer in senior football, he did not join Athletic until he was already 19 and arguably played his finest football in his 30s.
He won his first Spain cap in 2010 before earning a recall six years later at the age of 35, winning a spot in Vicente del Bosque's squad for Euro 2016.
Having decided to end his career after 2019-20, he started the season by scoring a stunning overhead kick to seal a 1-0 win over Barcelona at San Mames last August.
In so doing, he became the only player other than Lionel Messi to score in 15 LaLiga seasons in a row.
However, he only played a further 13 times in LaLiga - all as a substitute - and failed to score again.
Manchester United, Milan and Paris Saint-Germain are among the major European outfits who are due to farewell high-profile players when free agency comes into force on June 30.
Domestic leagues across the world appear increasingly likely to run beyond that deadline, meaning sides up and down the divisions could be forced to renegotiate deals beyond the typical expiry date.
It remains to be seen how governing bodies will approach the unfamiliar territory but Edinson Cavani, Mario Gotze and Zlatan Ibrahimovic will be watching closely like dozens more across Europe's top five leagues.
These are the stars and solid supporting cast members whose contract situations are worth monitoring in England, France, Germany, Italy and Spain.
LaLiga
Athletic Bilbao: Aritz Aduriz (retiring), Benat, Mikel San Jose
Atletico Madrid: Antonio Adan
Espanyol: Ander Iturraspe
Granada: Roberto Soldado
Real Valladolid: Hatem Ben Arfa
Sevilla: Ever Banega (joining Al Shabab at end of contract), Nolito
Valencia: Ezequiel Garay
Villarreal: Santi Cazorla
Premier League
Bournemouth: Ryan Fraser
Burnley: Joe Hart
Chelsea: Olivier Giroud, Pedro, Willian
Liverpool: Adam Lallana, Nathaniel Clyne
Manchester City: David Silva (confirmed he will leave at end of contract)
Manchester United: Nemanja Matic, Timothy Fosu-Mensah, Odion Ighalo (loan ends)
Newcastle United: Matty Longstaff
Tottenham: Jan Vertonghen, Japhet Tanganga
Serie A
Atalanta: Jose Luis Palomino
Hellas Verona: Fabio Borini
Inter: Ashley Young
Juventus: Gianluigi Buffon
Milan: Lucas Biglia, Giacomo Bonaventura, Zlatan Ibrahimovic
Napoli: Jose Callejon, Dries Mertens
Bundesliga
Bayer Leverkusen: Charles Aranguiz
Borussia Dortmund: Mario Gotze, Lukasz Piszczek
Hertha Berlin: Salomon Kalou
Schalke: Benjamin Stambouli
Wolfsburg: Robin Knoche
Ligue 1
Lille: Loic Remy
Monaco: Jemerson
Nice: Walter Benitez, Arnaud Lusamba
Paris Saint-Germain: Edinson Cavani, Thomas Meunier, Tanguy Kouassi, Layvin Kurzawa, Thiago Silva
The veteran striker, who has scored 172 goals in over 400 appearances for Athletic, announced his intention to retire at the end of this season back in August.
His final season as a player is set to be marked by an all-Basque Copa del Rey final between Athletic and La Real.
Originally scheduled to take place on April 18 in Seville, the Copa showpiece - along with the vast majority of sport around the world - has been put on hold.
It is not clear when the final will be played. However, Aduriz accepts even an occasion as momentous as the clash with La Real has little significance amid a crisis that has killed over 12,000 people in Spain.
"This coronavirus crisis is forcing us to think twice and consider what matters," Aduriz told Athletic's official website. "And now my retirement, or football in general, or if we will play [the Copa del Rey final] or not doesn't matter.
"I think there are many other more important things to stop and solve. I'm sure with everyone's help together, with each of us playing our role, we will get ahead of it. That's what I'm focused on at this moment and that's the most important thing."
Aduriz was born in San Sebastian, where Real Sociedad hail from, but he expects a respectful reception from their fans if and when the final goes ahead.
He added: "Maybe all of us are keeping in mind the Copa del Rey final, but we're prioritising other things now.
"We're all going through a tough time where many people are struggling a lot and even passing away…so, the final of the Copa has its importance, but maybe not that much now.
"There are other things we need to solve together, and if the day [of the final] finally comes, I'm Donostiarra [people originally from San Sebastian]. I've always felt very comfortable in Donostia [the city's Basque name] and that won't change whatever happens in any football game. I'm sure they will treat me in the same way, no doubt."
Asked about recognition for his achievements from Athletic fans, Aduriz replied: "If we've learned something from this pandemic or virus that we're struggling with, it's that we should think twice about what is important.
"I sincerely believe the people who really deserve a statue and recognition are clear nowadays, and it's not me or any football player.
"I would build a statue to those who are battling every day at the very front line against the virus in all the hospitals. They're showing us what really matters.
"We have to realise what's important and what isn't. And this is probably showing us that football isn't important enough for this kind of recognition."
