[1] It was the officially recognised undergraduate student representative body [2] of The University of Hong Kong until 13 July 2021 after the union's council passed a motion in memorial to a deceased assailant who attacked and severely stabbed a police officer on the street.

After the Second World War in 1945,[5] the Hong Kong University Students' Society[5] was formed on 13 November 1946 to "pave the way for the eventual resuscitation of the Union".

[6] Two years later in 1949,[5] the Union submitted a successful application for becoming a student organisation to the Hong Kong Police,[5] independent from the operation of the University.

On 7 July 2021, the Council of the Union passed a motion to "[express] its deep sadness at the death of Mr Leung Kin-fai; [offer] its sympathy and condolences to his family and friends; [appreciate] his sacrifice to Hong Kong".

[7] The individual mentioned in the motion assaulted a police officer with a knife and then killed himself immediately in Causeway Bay on 1 July 2021, during the 24th anniversary of the handover of Hong Kong.

On 13 July, the university issued a statement strongly condemned the act of "blatantly whitewashing violence" and has ceased recognising the role provided by the union on campus and their representation for the member students, subsequently ceased collecting membership fees from the students on behalf of the union.

All Union Council members were on the watch list and told they be intercepted should they attempt to leave Hong Kong.

[12] Four members of the Union Council were also arrested and charged of advocating terrorism under the national security law in August, they were later granted bail.

This marked the beginning of a permanent stance that the Chinese Communist Party should be held responsible for the June Fourth massacre in Tiananmen Square in Beijing in 1989.

Later in 2009, another General Polling passed stated that the Central People's Government of China should rehabilitate the June Fourth Massacre, and be held responsible for the deaths and casualties during the incident.

[17] As part of the construction of the Centennial Campus, the Hsü Long Sing Amenities Centre, where the HKUSU had resided for a number of years, was demolished in 2011.