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The Sumitomo group traces its roots to a bookshop in Kyoto founded circa 1615 by a former buddhist priest, Masatomo Sumitomo. Considered its spiritual founder, even today management of the group is guided by his "Founder's Precepts", written in the 17th century.
It was copper that made the company famous. Riemon Soga, Masatomo Sumitomo's brother-in-law, learned Western methods of copper refining. In 1590 he established a smelting business named Izumiya, literally meaning "spring shop". The advanced techniques, which Riemon perfected, allowed the extraction of silver from copper ore, something which Japanese technology had as yet been unable to accomplish.
The smelting and smithing business, which was begun in Kyoto, was moved to Osaka by the late 17th century. and Soga passed control of the company to his son Tomomochi who managed its transformation into a major trading house during the Edo period Sumitomo began to export copper, import silk, and provide financial services. By 1691 copper mining had been added to the portfolio.
The Meiji Restoration allowed Sumitomo to import and utilize Western machines and techniques in its mines. Sumitomo soon branched out into even more business areas entering the machine and coal industries, as well as the forestry, banking and warehousing businesses becoming a zaibatsu, or business conglomerate.
Sumitomo Group together with KDDI signed an agreement with Myanmar State owned Myanmar Post and Telecommunication (MPT) in July 2014 to jointly operate a mobile phone service in Myanmar for next 10 years. 
- Sumitomo Chemical, Chemicals
- Sumitomo Heavy Industries, Machinery, weaponry, and shipbuilding
- Sumitomo Precision Products, Precision Machinery
- Sumitomo Mitsui Banking Corporation, Finance
- Sumitomo Metal Industries, Steel
- Sumitomo Metal Mining Co Ltd, Non-ferrous metal
- Sumitomo Corporation, an integrated trading company
- Sumitomo Corporation of America
- Sumitomo Trust and Banking, now Sumitomo Mitsui Trust Holdings, Finance
- Sumitomo Life, Insurance
- Sumitomo Coal Mining Co Ltd, Mining
- The Sumitomo Warehouse Co Ltd, Warehousing
- Sumitomo Electric Industries, Ltd., Electronics and electric products
- Mitsui Sumitomo Insurance Co Ltd, Insurance
- Mezon Stainless Steel Fzco., Stainless Stockiest
- NEC Corporation, Electronics and electric products
- Nippon Sheet Glass Co Ltd, Glass
- Sumitomo Realty & Development Co Ltd, Real estate
- Sumitomo Osaka Cement Co Ltd, Cement
- Osaka Titanium Technologies Co Ltd
- Sumitomo Light Metal Industries Ltd, Nonferrous metals
- Sumitomo Mitsui Construction Co Ltd, Construction
- Sumitomo Bakelite Co Ltd, Chemicals
- Sumitomo Forestry Co Ltd, Lumber and housing
- Sumitomo Rubber Industries, Tires and rubber under Dunlop brand
- Sumitomo Riko, Industrial materials(Rubber) for Vehicles, Printers and Constructions
- Mazda Motor Corporation
- Presidio Ventures
- Sumisho Computer Systems (USA) Inc, Information Technology
- Sumitomo Electric Bordnetze, Auto parts suppliers
Sumitomo companies which are in the Nikkei 225
- NEC Corporation
- Sumitomo Chemical
- Sumitomo Corporation
- Sumitomo Electric Industries
- Sumitomo Heavy Industries
- Sumitomo Metal Industries
- Sumitomo Metal Mining Co Ltd
- Sumitomo Mitsui Financial Group
- Sumitomo Mitsui Trust Holdings
- Sumitomo Osaka Cement Co Ltd
- Sumitomo Realty & Development Co Ltd
- Company History Sumitomo Electric
- Sumitomo in History, part I: A Business Spirit Alive and Well After 400 Years, A Meeting with Copper Sumitomo Official Site
- Sumitomo Group, Encyclopædia Britannica article britannica.com
- Sumitomo in History, part II: Japanese Copper Across the Sea, Contributing to the Wealth of the Nation Sumitomo Official Site
- Sumitomo in History, part III: Japan's Kitchen, New Businesses Emerge Sumitomo Official Site
- About Us Sumitomo Corporation Official Site
- Sumitomo in History, part IV: Milestones, Major Copper Vein Discovered Sumitomo Official Site
- Sumitomo in History, part VI: A Time of Adversity, The End of Rule by the Samurai Sumitomo Official Site
- "KDDI, Sumitomo ink deal with Myanmar telecom for mobile phone service (17 July 2014)". http://english.kyodonews.jp. Kyodo News. Retrieved 17 July 2014.
- "KDDI, Sumitomo ink deal with Myanmar telecom for mobile phone service". http://www.japantimes.co.jp. The Japan Times. Retrieved 17 July 2014.
- TOP > Corporate Profile > Key events Osaka Titanium Technologies Official Site
- "Our Profile | Presidio". Presidiostx.com. Retrieved 2010-09-19.
- "Corporate History - Sumisho Computer Systems Corporation". Scs.co.jp. Retrieved 2010-09-19.
- (English) Sumitomo Group Public Affairs Committee
- (English) Company profile and the origins of Sumitomo Official Sumitomo Site