"Over the course of my mandate, I did quite a few things for Rio. For Brazil, in fact," the former Barcelona striker and 1994 World Cup winner told the Globo news website overnight.
"As senator, I think I'll have the chance to do more concrete things, specifically for Rio."
The 47-year-old was elected lawmaker for the Brazilian Socialist Party (PSB) in 2010 but distanced himself from the group in August.
However, he said he decided to mount a bid for the Senate after "a very good discussion" with PSB head Eduardo Campos, who is expected to run for president.
Since 2010, Romario has made a name for himself by being a disability rights advocate and repeatedly criticizing the high cost of sports events hosted by Brazil, including last year's FIFA Confederations Cup and the upcoming World Cup, which kicks off on June 12.
Football great Romario eyes Brazil Senate seat
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