The actor was a regular on the big screen at a time of racial segregation in the US, appearing in a Patch of Blue in 1965, and then Heat of the Night the year after, followed by Guess Who's Coming to Dinner, playing a black man with a white fiancée.
In Heat of the Night he portrayed Virgil Tibbs, a black police officer confronting racism during a murder investigation.
His other classic films included The Blackboard Jungle and A Raisin in the Sun, which he also performed on Broadway.
He went on to direct a raft of films, and a Broadway play about life and career was announced last month.
'Tackled racism head on'
Empire magazine's Amon Warmann told the BBC: "He was a pioneer, he's so influential and paved the way for so many in the industry to make their own mark, not least Denzel Washington, who paid tribute to him when he won an Oscar."
Washington, who won an Oscar in 2002 on the same night Poitier won an honorary Oscar, joked as he said: "Forty years I've been chasing Sidney and what do they do - they go and give it to him in the same night."
Warmann added that Poitier "tackled racism head on" in his work but was also "so versatile". "He really helped change the game for how black actors were viewed at that time [of his Oscar win]. He was one of the biggest stars during that period." Viola Davis, the first black American to win an Oscar, an Emmy and a Tony Award, said: "No words can describe how your work radically shifted my life."