Resonac (レゾナック株式会社, Rezonakku Kabushiki-gaisha), formerly Showa Denko K. K. (昭和電工株式会社, Shōwa Denkō Kabushiki-gaisha; abbreviated as SDK), is a Japanese chemical company producing chemical products and industrial materials. It was founded in 1939 by the merger of Nihon Electrical Industries and Showa Fertilizers, both established by a Japanese entrepreneur Nobuteru Mori.

Resonac's products serve a wide array of fields ranging from heavy industry to the electronic and computer industries. The company is divided in five business sectors: petrochemicals (olefins, organic chemicals, plastic products), aluminum (aluminum cans, sheets, ingots, foils), electronics (semiconductors, ceramic materials, hard disk drive platters), chemicals (industrial gases, ammonia, agrochemicals), and inorganic materials (ceramics, graphite electrodes). Showa Denko has more than 180 subsidiaries and affiliates. The company has vast overseas operations and a joint venture with Netherlands-based Montell and Nippon Petrochemicals to make and market polypropylenes. In March 2001, Resonac merged with Showa Denko Aluminum Corporation to strengthen the high-value-added fabricated aluminum products operations, and is today developing next-generation optical communications-use wafers.

Showa Denko is a member of the Mizuho keiretsu.

Hard Disc Media

Petrochemicals

Chemicals

Inorganics

Aluminum