From Tuesday, humans will be using up more of the Earth's resources than can be regenerated in an entire year.
The so-called Earth Overshoot Day has moved up by two months over the past 20 years and this year's date is the earliest ever, the study by the Global Footprint Network said.
The equivalent of 1.75 planets would be required to produce enough resources to meet humanity's needs at current consumption rates.
"The costs of this global ecological overspending are becoming increasingly evident in the form of deforestation, soil erosion, biodiversity loss, or the buildup of carbon dioxide in the atmosphere," the environmental group said.
"The latter leads to climate change and more frequent extreme weather events."
Some energy-hungry countries are overshooting even earlier - with America using up five planets worth of resources every year.
Australia follows closely, needing 4.1 planets to go around.
Calculated since 1986, the grim milestone has arrived earlier each year.
In 1993, it fell on October 21, in 2003 on September 22, and in 2017 on August 2.
"We have only got one Earth - this is the ultimate defining context for human existence. We can't use 1.75 (earths) without destructive consequences," Founder of GFN Mathis Wackernagel said.
Maria Carolina Schmidt Zaldivar, Chile's environment minister and chair of the Climate COP25 scheduled this December in Santiago, said a major cause of the date falling earlier and earlier was growing amounts of CO2 emissions.
"The importance of decisive action is becoming ever more evident," she said.
