A Manchester-born youth product of Manchester City, Mellor made himself a lifelong hero with Wednesdayites midway through his debut season at Hillsborough, when he opened the scoring in the 1979 "Boxing Day massacre" 4-0 home win over neighbours United with a goal from 25 yards. He also hit the woodwork in that game.
Despite being played in Division Three, the match was watched by over 49,000 fans - a record for third-tier football.
The goal is still occasionally sung about to this day.
"It's strange to me, considering it's 40-plus years ago, but it remains such a strong feeling among Wednesday supporters," he told The Sheffield Star three years ago. "It's flattering but crazy!
"You're only remembered so many years on if you're a good player and luckily for me I scored a good goal in such an important game."
Jack Charlton's Owls won promotion by finishing third that season and would be third in Division Two two years later, Mellor's final Hillsborough campaign.
After 11 goals in 79 appearance, he joined the Bantams, where he played his last two seasons at professional level before winding down with Hong Kong club Tsun Wan, Worksop Town, Matlock Town and Gainsborough.
Ian Mellor being congratulated by Mark Smith, Terry Curran and Jeff Johnson after giving Sheffield Wednesday a 1-0 lead against the Blades on Boxing Day 1979Earlier in his career, Mellor also played for Norwich City, Brighton and Hove Albion - the club he made most appearances for and where he gained his nickname "Spider - and Chester City.
He won the 1972 Charity Shield with Manchester City appearing as a substitute in a 1-0 win away to Division Three champions Aston Villa.
Ordinarily the game would have been between Division One champions Derby County and FA Cup winners Leeds United, but both declined invitations to play.
Mellor's son, Neil, also played for the Owls on loan from Preston North End in the 2010-11 season.
In announcing the news on Twitter, Neil referred to "My dad, my hero".
Ian Mellor had been suffering from amyloidosis, a rare disease which affects the internal organs.