Masatomo Sumitomo, the founder of Sumitomo, was born into a samurai family in 1585 in Maruoka of Echizen Province. He later opened a store in Kyoto, selling books and medicines, which marks the start of Sumitomo’s history.

Riemon Soga, along with Masatomo Sumitomo, created the foundation of today’s Sumitomo Corporation by starting a copper-processing business in Kyoto in 1590 under the trade name Izumiya. He established the copper-refining technology known as Nanban-buki (Western Refining).

In 1691, Sumitomo began mining operations in the Besshi Copper Mines after discovering a rich copper ore vein in Iyo. This marked the transition from copper trade to mining, establishing Sumitomo as a key player in Japan's copper industry.

In 1836, the Sumitomo trademark was inscribed on a pass required for entering and leaving the residences of powerful generals. This trademark symbolized Sumitomo for centuries but was forbidden for use after World War II by the occupation administration.

The Besshi mine railway, established in 1893, was one of the leading mine railways in Japan. Sumitomo acquired the first locomotive for the railway from Germany.

A reproduction of an award certificate from the Paris Exposition in 1900 showcased the achievements of Sumitomo during that time, highlighting their contributions to industrial development.

In December 1919, Sumitomo Corporation was originally founded as the Osaka North Harbour Company Limited. The company initially focused on real estate management and land reclamation in the Hokko area of Osaka.

In 1921, Sumitomo was reorganized as a limited partnership and renamed Sumitomo So-Honten.

In 1934, Sumitomo Heavy Industries was established as a separate company, specializing in steelmaking systems, heavy machinery, and ships.

The management of the Sumitomo Joint-stock Company and the Besshi Mining Company was divided to form Sumitomo Besshi Mining Co., Ltd.

Sumitomo Besshi Mining Co., Ltd. and Sumitomo Coal Mining Co., Ltd. combined to create Sumitomo Mining Co., Ltd.

In 1944, Sumitomo Corporation merged with Sumitomo Building Co., Ltd. to establish Sumitomo Building and Real Estate Co., Ltd. This merger brought together expertise in real estate management and construction, shaping the future of the company.

Production of electrolytic nickel commenced during the period of 1945 to 1946.

In January 1946, Nippon Engineering, under the leadership of Shunya Toji, established its head office sales department with only 32 staff members who were considered 'amateurs' in the trading business. Despite their lack of experience, Toji motivated them by emphasizing the power of enthusiastic amateurs.

During the postwar period in 1947, Shunya Toji, the president of Sumitomo Corporation, emphasized the effectiveness of enthusiastic amateurs over professionals in the trading division. He motivated employees to excel through passion and dedication.

In 1949, Sumitomo Building transitioned to general trading and changed its name to Nippon Engineering Co., Ltd. The firm listed its shares on the Osaka, Tokyo, and Nagoya Stock Exchanges, marking a new chapter in its existence.

In 1950, Sumitomo Corporation posted an employee to Bombay (now Mumbai) for the first time, marking the establishment of its first overseas presence. This move was part of the company's efforts to expand globally and solidify its management foundation.

In June 1952, Nippon Engineering Co., Ltd. changed its name to Sumitomo Shoji Kaisha Ltd., marking the rebirth of the corporate name 'Sumitomo' after it had been forbidden following the dissolution of the zaibatsu. This change propelled Sumitomo Shoji as the general trading company of the Sumitomo Group.

In September 1956, the company changed its name to Sumitomo Metal Mining Co., Ltd. and revived the original 'igeta' emblem.

In April 1960, the company founded Tokyo Electronic Metal Co., Ltd. to produce germanium dioxide and ventured into the electronic materials industry.

In 1962, the company relocated to the New Sumitomo Building, the largest building in West Japan at that time. This move also involved other Sumitomo affiliate companies, leading to the establishment of a dual-headquarters system with the Osaka Headquarters.

In April 1963, the company established Siporex Manufacturing Co., Ltd. to manufacture ALC (Autoclaved Lightweight aerated Concrete).

President Hisashi Tsuda wrote the Business Principles in January 1965, which became the foundation of Sumitomo's business philosophy. An English translation was introduced, and these principles continue to guide the sales activities of all Sumitomo Corporation Group companies.

In May 1966, Sumitomo Corporation announced its goal to become one of the 'Big Three' in the industry. Under Hisashi Tsuda's presidency, the company significantly expanded its business operations and sales volume, achieving remarkable growth.

In August 1967, the Central Research Laboratories, now known as Ichikawa Research Center, was completed.

On December 24, 1969, the company celebrated the 50th anniversary of its original establishment, The Osaka North Harbour Company Ltd. The ceremony took place at the New Sumitomo Building, where President Hisashi Tsuda expressed gratitude to predecessors and outlined future goals.

In June 1970, the New Niihama Nickel Refinery was completed.

In February 1971, the Toyo Smelter was completed.

In 1973, Sumitomo focused on strengthening its business structures during a major transition period.

In February 1977, Niihama Research Laboratories was founded, focusing on research and development activities.

In June 1978, the company changed its English name to Sumitomo Corporation to emphasize its role as a trading company and expand its trade business.

In 1982, Sumitomo reported an energy conservation program aimed at reducing energy consumption within the company.

In July 1988, the company and Sumitomo Corporation jointly invested in the Morenci Copper Mine in Arizona, which was owned by Phelps Dodge Corporation (now Freeport McMoRan Inc.).

In September 1988, the slogan 'Seeing Tomorrow, Innovating Today' was adopted, aiming to unite employees towards achieving an integrated business enterprise.

In 1991, Sumitomo Corporation formulated the medium-term management plan 'Strategy 95' with the aim of realizing the Integrated Business Enterprise vision.

In January 1992, the company participated in the Candelaria Copper Mine development project led by Phelps Dodge Corporation.

In 1994, Sumitomo Corporation promoted the development of a new earnings structure designed to respond to globalization under the slogan 'Global Mind, Global Reach'.

In September 1995, the company took equity participation in Jinlong Copper Co., Ltd. in China.

In 1996, Sumitomo Corporation faced a significant setback with the discovery of an unlawful copper trading incident, resulting in substantial financial losses. The company implemented stringent internal controls to prevent future occurrences, leading to a decade-long process until a final resolution was reached.

In February 1997, Sumitomo Metal Mining America Inc was established to manage the company's mineral resource business overseas.

In 1998, under the leadership of President Kenji Miyahara, Sumitomo Corporation introduced a new risk-adjusted return ratio to overcome the challenges posed by the unlawful copper trading incident. This strategic move positioned Sumitomo ahead of its competitors in risk management.

In September 1999, Sumitomo Metal Mining Siporex Co., Ltd. was established as a spin-off of the Building Materials Division.

In 2000, Sumitomo Corporation initiated the implementation of medium-term management plans to outline strategic goals and objectives for the company's future growth and development.

In May 2001, Sumitomo Corporation relocated its head office to Harumi Island Triton Square in Tokyo. This move followed the completion of the complex in April 2001, which included commercial facilities, halls, residences, and office wings X, Y, Z, W.

In June 2001, Sumitomo's President Motoyuki Oka introduced a medium-term management plan focused on setting regular objectives every two years. Oka emphasized the importance of strategies reaching the frontline workers, leading him to actively engage with work-sites to implement the plan.

In 2003, Sumitomo Corporation established the Sumitomo Corporation Corporate Governance Principles.

In December 2005, the company took equity participation in the Ojos del Salade Copper Mine project located in Chile.

In November 2006, the Cerro Verde copper mine started the production of copper concentrate.

Upon assuming the presidency in June 2007, Susumu Kato emphasized the importance of securing, training, and appointing exceptional human resources in overseas companies. This initiative aimed to enhance Sumitomo Corporation's global consolidated management, leading to the establishment of the Sumitomo Corporation Global HRD Center in Tokyo's Ginza district in April 2012.

In August 2009, the company acquired equity participation in the Nickel Asia Corporation based in the Philippines.

In September 2009, the company made the decision to implement the Taganito Project in the Philippines.

In May 2011, Sumitomo Corporation participated in the Sierra Gorda Copper Mine development project in Chile, which was operated by Quadra FNX Mining Ltd. (now known as KGHM International Ltd.).

In October 2011, Sumisho Computer Systems Corporation (SCS) merged with CSK Corporation to establish SCSK Corporation. This new entity focuses on promoting the digital transformation within the Sumitomo Corporation Group.

Kuniharu Nakamura, assumed presidency in June 2012, created a vision for Sumitomo Corporation in preparation for its 100th Anniversary in 2019. The company also introduced a new slogan 'Be the Best, Be the One' to signify its commitment to sustained growth in the coming decades.

In September 2013, Mitsui Mining & Smelting Co., Ltd. and Sumitomo Metal Mining Co., Ltd. consolidated their copper and copper alloy fabricated businesses.

In September 2014, Sumitomo Corporation entered the telecommunications sector in Myanmar, with plans to expand into other Asian countries. The aim is to offer value-added services that enhance subscribers' lives.

In 2015, Sumitomo Corporation launched a new medium-term management plan titled 'Be the Best, Be the One 2017'. The plan aimed to guide the company in addressing challenges and setting a course towards achieving its goals.

In February 2017, Sumitomo Corporation acquired Fyffes Ltd, a fresh produce business operating in Europe and the Americas. This move expanded the company's portfolio in the agricultural sector.

In April 2018, Masayuki Hyodo became the president of Sumitomo Corporation Group and introduced the growth strategy 'Medium-Term Management Plan 2020' focusing on 'Unceasing Challenge for New Value Creation.'

In September 2018, Sumitomo Corporation Group relocated its head office to the Otemachi district in Tokyo's Chiyoda Ward, aiming to enhance convenience and revamp employee working styles for a more efficient and creative office environment.

On December 24, 2019, Sumitomo Corporation Group commemorated its 100th founding anniversary, marking a significant milestone in the company's history.

Over the 12-month period ending in August 2020, Berkshire Hathaway acquired over 5% of Sumitomo's stock, along with shares in four other Japanese trading houses.