he had suffered complications during surgery.
Gloucestershire said the club's flag would be lowered to half-mast until the start of the County Championship season on 5 April.
"Mike was a fantastic player and quite rightly regarded as one of the best all-rounders that has ever represented Gloucestershire," former team-mate David Graveney said.
"I don't think people realise that when Mike played he was playing through great pain in his knee, but that didn't stop him from performing at the level he did.
"The phase 'Proctershire' was very apt for Mike. He put in the biggest performances in the biggest games."
Procter was on the winning side in six of the seven Tests he played - all against Australia - between 1967 and 1970 and took 41 wickets at an average of just 15.02 before his international career was cut short.
His reputation as a formidable fast bowler was well earned and in 401 first-class games from 1965 to 1988, he took 1,417 wickets at 19.53, with a further 344 wickets at 18.76 in List A cricket.
He won the Gillette Cup and the Benson and Hedges Cup in his time with Gloucestershire, captaining them to the latter, and in 2020 was voted the county's greatest overseas player.
Procter was Proteas coach from 1991 to 1994 and he led the side to the semi-finals of the 1992 World Cup.
He later became an International Cricket Council match referee.
He forfeited the Oval Test between England and Pakistan in 2006 when the away side refused to return after the tea break having been penalised for ball-tampering by the umpires.
Procter also banned India's Harbhajan Singh for three Tests in 2008 for allegedly racially abusing Australia all-rounder Andrew Symonds. The ban was lifted soon afterwards when the charges were downgraded to the use of abusive language.