According to a Federal Election Commission filing, Chelsea Elizabeth Manning filed her candidacy papers on Thursday.
The election document lists Manning's address as that of a luxury apartment tower in North Bethesda. Cardin is relied upon to a win the race to serve a third term. She was convicted by court-martial in 2013 of espionage and other offenses for furnishing more than 700,000 documents, videos and diplomatic cables to WikiLeaks, an global organization that publishes information from anonymous sources.
Manning leaked more than 700,000 government documents to WikiLeaks because she believed she had a responsibility to the public, she has said.
President Barack Obama granted clemency to Manning before leaving office.
Chelsea Manning has filed to run for the U.S. Senate in Maryland.
Manning, who entered an all-male military prison as "Bradley", announced he was transgender immediately after his sentencing in 2013.
Manning has been active in advocating for LGBT and other causes since being released earlier this year.