The Confederation of Trade Unions (CTU) said on Sunday that its members would discuss and vote on a motion to disband on October 3.
Leaders of CTU said they had received messages that if they continued to run the group, their personal safety might be at risk.
Its vice president, Leo Tang, said they felt terrified, but he said he could not divulge any more details.
“We cannot tell the details on what kind of messages we have got and lead us to the decision. We are sorry about that. We really couldn’t tell the details. But it is clear for our leadership that we feel terrified,” he said.
He also denied allegations that the group had been colluding with foreign forces, saying they had merely cooperated and communicated with international unions on labour rights issues.
CTU's chief executive, Mung Siu-tat, announced on Saturday that he had resigned from the post and had left Hong Kong urgently, citing personal safety.
The umbrella union was founded in 1990. It says it currently represents more than 80 affiliates from various sectors.
The announcement came after the Professional Teachers' Union and the Civil Human Rights Front dissolved.