General Qassem Suleimani, commander of the Quds Force, the foreign operations arm of Iran's Revolutionary Guards, won 37 percent of the votes cast in the survey to mark the Persian New Year, Nowruz.
Once rarely seen, Suleimani is now frequently pictured in social media near the front line in Iraq and has been spotted close to this week's battles in Tikrit.
He has become the public, if unofficial, face of Iran's support for the Iraqi and Syrian governments against IS jihadists, reportedly landing in Baghdad hours after IS overran Iraq's second city Mosul last June.
Suleimani beat last year's winner, Foreign Minister Mohammad Javad Zarif, in the poll, which is conducted by KhabarOnline, a moderate conservative news website.
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Zarif, who heads Iran's negotiating team in nuclear talks with the world powers, scored 28 percent this year.
According to KhabarOnline, 463,000 votes were cast between March 7 and March 14, with the results being released one week before Nowruz, which falls on March 21.
Popular pop singer and composer Morteza Pashaei, who died from cancer in November aged just 30, placed third in the poll with 18 percent.
Outspoken conservative member of parliament Ali Motahari came fourth with 13 percent.