The woman in jail has not been named, but it is believed that she is the Instagram queen Shirin Nobahari.
The judiciary’s news agency said: “One of the female bodybuilders who recently published nude photographs on social networks has been arrested.”
Ms Nobahari, who used the Instagram name Shirin Muscleking, is seen as a social media star in Iran.
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In Iran, ‘nude’ can refer to a woman who is not wearing a headscarf or is revealing parts of her body such as arms and legs.
The woman who was arrested is being held in prison as she reportedly could not afford to pay the bail, which was £41,000.
Although Iranian woman are allowed to take part in international sporting events, they must respect Islamic rules on clothing at all times.
The bodybuilder has previously been warned about posting selfies that have been deemed “un-Islamic”.
Female swimmers have to wear full bodysuits and headscarves and women footballers and athletes have to wear tracksuits and long sleeves.
There have also been incidents where female sports fans were arrested for watching male sports events.