Cheung distinguished himself with the successful defence of his Olympic title in the men's individual foil while Haughey won a consecutive medal in the 200 free.
Hong Kong, China now ranks tenth in the medals table with China third in the tally with five golds thanks to efforts from their divers and shooters. Japan top the table ahead of hosts France.
Here's a look at what happened.
Edgar gets the job done
Edgar Cheung won a closely fought 15-14 final against Italy's Filippo Macchi. He came from 11-14 down to tie the score at 14-14 before claiming the final point in a bout that went down to the wire.
Cheung becomes the first Hongkonger to defend an Olympic title and the first man since 1956 to defend a gold in foil.
Siobhan Haughey wins battle for bronze
Swimming star Siobhan Haughey was up against some tough competition in the final of the women's 200m freestyle.
The Aussie pair of Ariarne Titmus and Mollie O'Callghan battled for gold with O'Callaghan prevailing against Titmus while Haughey held on to win bronze.
Earlier, Cindy Cheung was eliminated in the women's 100m backstroke, finishing 29th overall in the heats.
HK's table tennis team still in the medal hunt
Hong Kong table tennis stars Doo Hoi-kem and Wong Chun-ting will play for a mixed doubles bronze, after losing to North Korea's pair 3-4 in the semi-finals.
Earlier, Wong Chun-ting advanced to the last-32 of the men's individual competition while Zhu Chengzhu made it through to the next round of the women's individual event.
There was disappointment for Lo Sin-yan in women's badminton after she lost her opening singles match to Brazil's Juliana Viana Vieria.
China cements diving dominance
China's Lian Junjie and Yang Hao claimed the men's synchronised 10 metre platform diving title.
They lived up to expectations by scoring a total of 490.35 points from six rounds in the final.
More gold for China on the shooting range
China's Sheng Lihao claimed the Paris Olympic title in the men's 10m air rifle event, adding to his victory in the 10m air rifle mixed team event along with Huang Yuting.
Sheng, the silver medalist from Tokyo, set an Olympic record with a score of 252.2 points at the Chateauroux Shooting Center.
Japan prevail in nail-biting men's team final
In other Olympic action, there was an exciting finale to the men's gymnastics team final as Japan edged out China by the slimmest of margins, with the Americans taking bronze.
