Maria Butina, the only Russian arrested and convicted in the three-year investigation of Moscow's interference in US politics, was sentenced to 18 months in prison on Friday.
The leader of a small Russian gun rights group, Butina used her ties to the NRA firearms lobby to build a network of powerful Republican contacts.
"I humbly request forgiveness. I'm not this evil person depicted in the media," she told the court in Washington before she was sent down.
Butina was given the full term requested by prosecutors, however, after previously admitting one count of conspiracy to act as an agent of a foreign government without registering.
The 30-year-old faces another nine months in custody, having already served half her term.
Prosecutors said that although she worked openly and was not tied to any Russian intelligence agency, she was nevertheless a threat to the United States.
"I wanted a future here in international policy," she said, voice breaking. She added that she only wanted to work towards better US-Russian relations.
"If I had known to register as a foreign agent I would have done so," she told the court.