The Hamilton fighter won Scottish, British, European and Empire titles before defeating Italy’s Salvatore Burruni at Wembley over 15 rounds to land the world flyweight title in 1966.
In McGowan’s next fight, he won the British and Empire title at bantamweight when he defeated Alan Rudkin, again at Wembley.
He won 32 of his 40 professional fights before retiring in 1969.
McGowan had been in poor health in recent years and was living in a nursing home in Bellshill.
He died peacefully at Monklands Hospital on Monday night.