The race was originally scheduled to take place in London on Sunday, 26 April.
"The world is in an unprecedented situation, grappling with a global pandemic of Covid-19, and public health is everyone's priority," said event London Marathon director Hugh Brasher.
"We know how disappointing this news will be for so many - the runners who have trained for many months, the thousands of charities for which they are raising funds and the millions who watch the race every year," he added.
"We know that there will be many, many questions from runners, charities and others and we ask you to please bear with us as we work through the detailed planning process to deliver the 2020 London Marathon on its new scheduled date."
The London Marathon was also scheduled to include Great British team trials for Tokyo Olympics. British Athletics is planning to arrange a different marathon trial for the Tokyo Olympics for the end of April.
London Marathon is the latest sporting event to be canceled in order to limit the spread of the coronavirus.
Earlier this week in the United States, NBA, NHL, and NCAA suspended their seasons. In Europe, UEFA suspended the Champions League and ULEB suspended Euroleague.
According to the World Health Organization, more than 132,500 people have been infected with Covid-19 in 123 countries around the globe. The total number of deaths worldwide is at least 5,000.