The Morocco-born athlete, who turns 31 next month, revealed her decision in a Facebook post on Saturday.
"There are stories that seem as though they will last forever. Then one day comes the moment when you have to write the final full stop. Today I am ending my sporting career," Ennaoui wrote.
Reflecting on her career, she said athletics had given her far more than medals and records, teaching her patience, humility, courage and perseverance.
"It also showed me how important it is to know when to stop, look around and truly appreciate the moments you worked so hard to achieve," she wrote.
Ennaoui won silver in the women's 1,500 metres at the 2018 European Championships and bronze in 2022.
Photo: PAP/Adam Warżawa
She also claimed silver at the 2019 European Indoor Championships, along with bronze medals in 2017 and 2023, all in the 1,500 metres.
At the national level, Ennaoui won Polish indoor titles in the 1,500 metres in 2015 and 2018, and in the 3,000 metres in 2017.
Her career was repeatedly disrupted by injuries and health problems, but she remained one of Poland's leading middle-distance runners over the past decade.
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Source: PAP