Kenneth Tsang, 87, was discovered by hotel staff two days after returning from Singapore, several outlets reported, including Now News, the South China Morning Post and the Oriental Daily.
Police said around noon (0400 GMT) they were informed that a "body" had been discovered by hotel workers.
The deceased was an 87-year-old man named Tsang, according to the incident report.
For Hong Kongers and Cantonese film fans, Kenneth Tsang was a household name actor, thanks to a career that spanned six decades and more than 200 roles listed in the IMDB film database.
While he began acting in earnest in the 1960s, his most memorable roles were performed during Hong Kong's golden era of cinema in the 1980s and 1990s in films such as The Killer, Supercop, Peking Opera Blues and Once A Thief.
He was also one of the few Hong Kong stars of that era to break into Hollywood playing supporting roles, mostly villains, in films like The Replacement Killers, Die Another Day - a James Bond Film - Anna and the King and Memoirs of a Geisha.
In what appears to be his final interview, Kenneth Tsang told Sin Chew Daily that he had just returned from a two-week trip to Malaysia and flew back to Hong Kong via Singapore.
He said he relished the solo trip after being looked after by others on nearly every previous trip in his life.
"I will do a quarantine if necessary," he told the newspaper.
Like China, Hong Kong has adopted a zero Covid strategy, including closing its borders to foreign travellers.
For residents, a period of isolation in a quarantine hotel is mandatory.
For much of last year the period was 21 days, recently it was reduced to seven days.
© 2022 AFP