The meeting in Liverpool, northwest England, would have been the first under the leadership of Keir Starmer, who was elected to replace Jeremy Corbyn in April.
"Our priority is the safety of members, staff and visitors to our events and the need to protect the public's health," a spokeswoman for the centre-left party said.
"In light of the ongoing coronavirus pandemic, we have therefore decided to postpone this year's annual and women's conferences."
The annual conference normally draws around 13,000 people, Labour said.
The British government introduced a nationwide lockdown at the end of March to slow the spread of COVID-19, which is only gradually now being eased.