Maggi, who is also governor of Mato Grosso state, secured 10,348 votes out of 27,849 cast in an Internet poll, Greenpeace said on its Web site on Monday. Brazilian President Luiz Inacio Lula da Silva was runner-up with 7,314 votes.
"Maggi deserved the award. After two years as the state governor, he has turned Mato Grosso into the state champion of deforestation, responsible for 48 per cent of the total forest loss in the Brazilian Amazon," Greenpeace Amazon coordinator Paulo Adario said.
Comedians from the Brazilian show "Panic on TV" had tried to present the award to Maggi at a school in Mato Grosso but they were removed by security, Greenpeace said.
The candidates were chosen because either their action or inaction had contributed to an alarming rate of deforestation, the group said.
The rain forest lost an area of 10,088 square miles (26,130 square km) in the year ending in August 2004, the second-highest level on record. The land is usually cleared first by loggers then taken over by ranching or other farming interests.
Maggi, whose Amaggi Group is the world's largest soybean producer, was not available for comment. In an interview with Reuters last month he said, "I am not the rapist of the forest."