The British star died at his home in California from natural causes, surrounded by his family, his son Robert confirmed.
The actor, who played John Steed in the 1960’s television spy series, was also a star of the stage, having appeared in theatre roles in both London’s West End and on Broadway.
A statement on the actor's website read: "Patrick Macnee was a popular figure in the television industry. He was at home wherever in the world he found himself. He had a knack for making friends, and keeping them. Wherever he went, he left behind a trove of memories and good wishes.”
Born in London, Macnee grew up in Berkshire and was educated at Eton College.
He served in the Royal Navy during World War Two, working on torpedo boats in the English Channel and the North Sea.
After the war, he took on a number of small roles in film and TV including one in Laurence Olivier's 1948 film version of ‘Hamlet’ - before rising to fame in the original ‘Avengers’ series between 1961 and 1969.
The series developed a cult following around the world, and saw him starring opposite the likes of Joanna Lumley, Gareth Hunt and Honor Blackman.
His character was known for his signature style of a bowler hat and umbrella, which was used as a secret weapon.
He also appeared in the 1985 James Bond film ‘A View to a Kill’, alongside Roger Moore as 007.
Sir Roger tweeted: "So very sad to hear Pat Macnee has left us. We were mates from 1950s and I have so many happy memories of working with him. A true gent."
So very sad to hear Pat MacNee has left us. We were mates from 1950s and I have so many happy memories of working with him. A true gent.— Sir Roger Moore (@sirrogermoore) June 25, 2015