Former badminton Olympic gold winner Marin retires due to injury
The 32-year-old won gold in the women's singles at the 2016 Rio de Janeiro Olympic Games, and remains the only player from a non-Asian country to do so.
Three-time world champion Marin had hoped to compete in the European Championships in April in Huelva, her home city in Andalucia, but did not want to risk further damaging her knee.
At the Paris Olympics in 2024 she reached the semi-finals but suffered a knee ligament injury during the match which forced her to withdraw, having already missed the 2020 Tokyo Olympics with another knee injury.
"My journey in professional badminton has come to an end," said Marin in a post on Instagram.
"I would have liked to see each other on court one last time, but I don't want to put my body at risk for it...
"I wish my career had ended another way but in life things don't always go as we want and we have to accept that.
"Deep down I did retire on court, in Paris in 2024, we just didn't know it at the time."
As well as winning gold by overcoming India's PV Sindhu in the Rio final, the tenacious Marin triumphed three times at the World Championships, in 2014, 2015 and 2018.
The latter of those finals was also against Sindhu, as Marin became the first woman to win three world singles titles.