The Shōwa era (Japanese: 昭和,Hepburn: Shōwa) refers to the period of Japanese history corresponding to the reign of Emperor Shōwa (Hirohito) from December 25, 1926 until his death on January 7, 1989. It was preceded by the Taishō period.
The pre-1945 and post-war Shōwa periods are almost completely different states: the pre-1945 Shōwa era (1926–1945) concerns the Empire of Japan, while post-1945 Shōwa era (1945–1989) is the State of Japan.
The two kanji characters in Shōwa (昭和) were from a passage of the Chinese Book of Documents: 百姓昭明，協和萬邦 (Translated: "[T]he people (of his domain), ... all became brightly intelligent. (Finally), he united and harmonized the myriad states.") From this same quotation, Japan also adopted the era name Meiwa (明和) during the Edo period in the late-18th century. There were two other candidates at the time - Dōwa (同和) and Genka (元化).
The term could be roughly understood as meaning "enlightened peace" or in some interpretations "radiant Japan".