The Richmond Park MP, who ran for London Mayor earlier this year, called the decision to approve the runway "catastrophic" and has now reportedly said he will quit his Commons seat withing 48 hours.
In a Tweet, Mr Goldsmith said: "Following the Government's catastrophic Heathrow announcement, I will be meeting my constituents later today before making a statement."
During a debate in parliament following the decision, Mr Goldsmith put forward his 'absolute opposition' to the Heathrow expansion.
Today (October 25) the government backed the third runway after decades of delays.
Transport secretary Chris Grayling said it was a "momentous" step, although the government's backing will be subject to public consultation and has been heavily criticised by campaigners.
Mr Grayling said: "The step that government is taking today is truly momentous."
"A new runway at Heathrow will improve connectivity in the UK itself and crucially boost our connections with the rest of the world, supporting exports, trade and job opportunities.
"This isn’t just a great deal for business, it’s a great deal for passengers who will also benefit from access to more airlines, destinations and flights.
"This is an important issue for the whole country."