Maria Butina, who served nine months in a US jail for acting as a Russian government agent, arrived in Moscow on Saturday, a day after her release from prison.
Butina arrived at Moscow's Sheremetyevo airport after leaving Miami, AFP journalists said. She had been held in Florida's Tallahassee prison.
She was arrested in July 2018 on allegations of engaging in espionage. In December, Butina entered a plea deal on a charge that she acted as an illegal, unregistered foreign agent, and was sentenced to 18 months in prison, half of which was credited as already served.