The Old Firm generates almost £120m a year for the economy and create thousands of jobs for Scotland, according to a new report.
Old Firm football fans provide millions of pounds for the economy
The University of Strathclyde's Fraser of Allander Institute looked at the monetary impacts of Celtic and Rangers during the 2003/4 season.
It found they generated triple the cash brought in by the Edinburgh festivals, creating 3,056 jobs along the way.
The figures include cash spent by fans at matches, as well as travel and food.
The survey found the Scottish teams helped create employment mainly within hotels, pubs and catering,
The employment figure included the 876 staff who work directly for the two clubs.
The Old Firm also helped generate £118m within Scotland through wages, salaries, sponsorship and profits, the study said.
The research was commissioned by the Glasgow City Marketing Bureau and found 75% of total expenditure by fans was in Glasgow.
A total of 63% of this went straight into the clubs' coffers with 37% going on food and drink, travel and hotels.
Rangers and Celtic fans living in Glasgow spent £15m annually as a result of matches compared to the £57m spent each season by supporters from the rest of Scotland.
Meanwhile, supporters south of the border also made a valuable contribution bringing in £22m to the economy, which equated to 23% of supporter expenditure.
Professor Kim Swales, who led the research, said: "This underlines just how important the Old Firm is to Scotland.
"Imagine a factory closing with the loss of over 3,000 jobs. That is what would happen if the two clubs ceased to be."
In comparison, the net income from the international arts events in the Scottish capital for August 2004 was around #38 million, with employment of 2,900.
Celtic chief executive Peter Lawwell said: "We are pleased the study confirms the positive impact of the Old Firm and demonstrates the huge contribution which both clubs make to the Scottish economy."
Rangers chief executive Martin Bain added: "This report demonstrates both clubs are institutions and have a huge influence on society, not just in terms of finance but also in wider terms in the community."
The researchers sent questionnaires to 200 suppliers and 4,000 season ticket holders for the study.