Chelsea Manning, the transgender former Army private who was convicted of passing sensitive government documents to Wikileaks, has filed to run for the US Senate in Maryland, according to federal election filings.

Manning, who did not immediately respond to a request for comment, would be challenging Democrat Senator Ben Cardin, who has served two terms in the Senate and is up for re-election in November. Cardin is Maryland's senior senator and is considered an overwhelming favorite to win a third term.

Manning, 30, who is formerly known as Bradley Manning, was convicted in 2013 of the largest leak of classified documents in US history and was sentenced to 35 years in prison. Last year, then-President Barack Obama commuted Manning's sentence to time served, and she was released from a military prison in Kansas.

Chelsea Manning addresses a forum in Nantucket in September 2017. Credit:AP

The news of Manning's filing caught Maryland's political class by surprise Saturday afternoon. It was first reported in a tweet by conservative media outlet Red Maryland.