Satellite imagery analyzed by Brazil's National Institute for Space Research showed 578 square kilometers (223 square miles) of Amazon woodland was burned or cut down.
That was more than four times the devastation recorded in May, and roughly equivalent to the size of Switzerland's Lake Geneva, or half the area of California's biggest city of Los Angeles.
Most of the destruction was concentrated in the Brazilian states of Para and Mato Grosso. Ranchers and farmers regularly encroach on the vast zone.
Between July 2008 and June 2009, more than 4,700 square kilometers of Amazon jungle has disappeared, according to the space agency's imagery.
Brazil last December vowed to slow the rate of deforestation in the Amazon, the world's biggest tropical woodland, by 70 per cent over a decade.