Leonard was taken to hospital earlier this week to be treated for a lung condition, reported to be obstructive pulmonary disease. The actor was a heavy smoker although he quit in his 50s.
His wife, Susan, confirmed to the New York Times that Leonard had died at their home in Los Angeles.
Alongside his role as Spock, Leonard starred in Mission Impossible and hosted a TV series, In Search Of…, between 1976 and 1982.
Tributes have been pouring in since the news broke this afternoon.
Jeff Parker wrote on Twitter: “Well this will be all we talk about now. Thanks for everything, Leonard Nimoy. My entire childhood and on, you were greatness,” while others simply wrote the phrase he made famous: “Live long and prosper”.
Some have hailed his last tweet, posted just four days ago as ‘perfect.’
A life is like a garden,” he wrote. “Perfect moments can be had, but not preserved, except in memory. LLAP”.