Just 22.1 million people travelled through the airport last year, down 58.8 million on the previous 12 months.
In December, numbers fell by 82.9% to 1.1 million, amid a new Covid strain.
It was announced last week that all travellers to the UK will have to test negative for coronavirus before they can enter the country.
Passengers arriving by boat, train or plane, including UK nationals, will have to take a test up to 72 hours before leaving the country of departure.
The new rules are expected to come into force later this week.
Heathrow chief executive John Holland-Kaye said: "The past year has been incredibly challenging for aviation.
"While we support tightening border controls temporarily by introducing pre-departure testing for international arrivals, as well as quarantine, this is not sustainable.
"The aviation industry is the cornerstone of the UK economy but is fighting for survival. We need a road map out of this lockdown, and a full waiver of business rates."
Passenger numbers at Heathrow dropped by almost three-quarters in 2020 as a result of the coronavirus pandemic, the airport said.