was the lead ship of the four-member of heavy cruisers of the Imperial Japanese Navy (IJN), which were active in World War II. She was named after Mount Myōkō in Niigata Prefecture. The other ships of the class were , , and .
Background
Myōkō was approved under the 1922–1929 Fleet Modernization Program, as the first heavy cruiser to be built by Japan within the design constraints imposed by the Washington Naval Treaty, and was the first of the "10,000 ton" cruisers built by any nation. Naval architect Vice Admiral Yuzuru Hiraga was able to keep the design from becoming dangerously top-heavy in its early years by continually rejecting demands from the Imperial Japanese Navy General Staff for additional equipment to the upper decks. During modifications and rebuildings in the 1930s, though, the final displacement rose to 15,933 tons, well over the treaty limits.
Design
thumb|left|Launch of Myōkō, April 16 1927
The Myōkō class displaced , with a hull design based on an enlarged version of the . Myōkō was long, with a beam of and draft of , and was capable of . Although the first ship in her class to be laid down, she was the third to be completed.
Myōkō was repeatedly modernized and upgraded throughout her career to counter the growing threat of air strikes. She eventually mounted 52 Type 96 25 mm AT/AA Gun guns and two Hotchkiss M1929 machine gun| antiaircraft guns after her final upgrade.
During the Second Sino-Japanese War, Myōkō participated in the Amoy Operation from 10–12 May 1938 as flagship of Sentai-9 of the IJN 5th Fleet along with the Hainan Island Operation in February 1939.
A second reconstruction and retrofit was completed in April 1941, doubling the number of torpedoes to 16, adding another eight 25-mm antiaircraft guns, and bulges to the hull to improve stability.
Later in March, Myōkō received a refit at Sasebo Naval Arsenal. In April, she participated in the unsuccessful pursuit of the Doolittle raid task force.
Battle of the Coral Sea
In May, Myōkō was part of the carrier strike force during the Operation Mo that resulted in the Tulagi invasion force and subsequently the Battle of the Coral Sea. She served as a flagship of Vice Admiral Takagi, who was in the overall command of the carrier strike force, which consisted of the aircraft carriers and , which were under a tactical command of Rear Admiral Chūichi Hara, the heavy cruisers Myōkō and Haguro, and five destroyers. Shōkaku was damaged by American aircraft and Zuikaku lost most of her aircraft in the Battle of the Coral Sea, forcing the flotilla to withdraw without invading Port Moresby.