The 46-year-old actor – who won an Oscar for his role in Capote in 2005 – was found dead in his New York apartment from an apparent drugs overdose.
According to the New York Post newspaper, Philip was found by his assistant at around 11.30 this morning in the bathroom of his apartment in Greenwich Village with a hypodermic needle still in his arm.
The assistant called police who are currently at the scene investigating what happened. An official cause of death has yet to be established.
Philip had struggled with substance abuse in his early career, and first went to rehab after graduating from New York University in 1989.
Many have rushed to pay their respects to the star, widely regarded as one of the finest actors of his generation.
Mia Farrow wrote on Twitter: “OH NO!!!!! Philip Seymour Hoffman has died. A truly kind, wonderful man and one of our greatest actors – ever.”
Actress Andie MacDowell added: “Phillip Seymour Hoffman was not only a genius actor but a kind, generous man RIP.”
Philip is survived by his partner, costume designer Mimi O’Donnell, and their three children: Tallulah, seven, Cooper, ten and Willa, five.
Film director Kevin Smith was also upset by the news, writing: “This truly blows. PHILIP SEYMOUR HOFFMAN has died … First noticed him in SCENT OF A WOMAN. Brilliant actor. So sad…(sic)”
Elijah Wood wrote: “Heartbroken and shocked. what a true loss. rest in peace, Philip Seymour Hoffman (sic)”
Comedy actor Jim Carrey added: “Dear Philip, a beautiful beautiful soul. For the most sensitive among us the noise can be too much. Bless your heart.”
Philip was highly regarded by actors, directors and audiences and brought a very distinctive presence to the roles he played in films including Doubt, Synecdoche, New York, Red Dragon, Almost Famous, The Talented Mr. Ripley and Capote– for which he won the Best Actor Oscar in 2005.
Philip was last seen on the big screen as Plutarch Heavensbee in The Hunger Games: Catching Fire, and he had been working on a new comedy-drama TV series, Happyish at the time of his passing.