United played 548 games with him in charge, making him the club's longest serving manager ever.
A statement released by Scunthorpe United read: Everyone at Scunthorpe United is mourning the passing of former manager Ron Ashman who has died at the age of 78.
"Ron was a very good friend and passionate supporter of Scunthorpe United and we shall all miss his smiling face and unrelenting enthusiasm.
"All at Scunthorpe United offer their deepest sympathis to Mr Ashman's wife Maragaret, and to his family."
He was a distinguished professional player with Norwich City, captaining the Canaries to the FA Cup semi-final in 1959 and promotion to the Second Division in 1960.
In 19 years with the club he played 662 times, before becoming their manager. He eventually left them in 1966, 22 years after arriving as an amateur player.
The following year he arrived at the Old Showground, and despite tight financial restraints brought promotion to the Third Division in 1972.
His first spell ended twelve months later when the Iron were relegated and he headed east to Blundell Park.
The discovery of 17-year-old Kevin Keegan will be Ashman's great contribution to football.
Keegan made 124 appearances for the Iron, scoring 18 times, before being snapped up by Biill Shankly's Liverpool for a bargain £33,000 in 1971.
After two years with Grimsby Ashman returned to the Iron in January 1976, saving the club from relegation.
In 1981 he was replaced by John Duncan and became general manager, before leaving the club in 1982.
He went on to become a travel agent with a shop in Scunthorpe High Street.
The club made him vice-president and he was still a regular at Iron games, as well as religiously attending AGMS and shareholder meetings.