State news agency PAP said a government source had confirmed the report.
The hospital will initially have 500 beds, with the number to be significantly increased later, according to wp.pl.
It added that the Polish army was helping to build the facility at the National Stadium, a prime venue for sports events next to the Vistula river.
wp.pl reported that a decision on building further field hospitals is to be made in the coming days.
Poland on Saturday reported a new daily record of 9,622 coronavirus cases, the highest figure since the epidemic hit the country in March.
Tougher measures to battle COVID-19 come into force in Poland the same day, with the number of “red” zones - those with the most severe restrictions - increased to cover almost half the country.
(pk)
Source: wp.pl/PAP