Miyako is located in central Iwate Prefecture, bordered by the Pacific Ocean to the east, with the main urban area fronting on Miyako Bay. It is connected to Morioka by an east-west train line and highway and the coastal highway also goes through the town. The city has a small port but much of the shipping traffic is taken by larger cities along the coast. Parts of the coastal area of the city are within the borders of the Sanriku Fukkō National Park, and part of the mountainous interior is within Hayachine Quasi-National Park. Over 80% of the city area is covered by mountains and forest. The easternmost point of Honshu island is at Cape Todo (魹ヶ崎, Todogasaki) in Miyako.
Miyako has a humid climate (Köppen climate classification Cfa) characterized by mild summers and cold winters. The average annual temperature in Miyako is 10.9 °C. The average annual rainfall is 1282 mm with September as the wettest month and February as the driest month. The temperatures are highest on average in August, at around 22.9 °C, and lowest in January, at around 0.2 °C.
Per Japanese census data, the population of Miyako has declined over the past 40 years.
The area of present-day Miyako was part of ancient Mutsu Province, and has been settled since at least the Jomon period. The area was inhabited by the Emishi people, and came under the control of the Yamato dynasty during the early Heian period with the construction a fortified settlement on the coast. During the Muromachi period, the area came under the control of the Nambu clan, and was the main seaport for Morioka Domain during the Edo period under the Tokugawa shogunate. During the Boshin War of the Meiji restoration, the Battle of Miyako Bay was one of the major naval engagements of the war.
Under the Meiji period establishment of the modern municipalities system, the towns of Miyako and Kuwagasaki were established within Higashihei District. The area was devastated by a 18.9 metres (62 ft) tsunami in 1896, which killed 1859 inhabitants. Higashihei District became part of Shimohei District on April 1, 1897. Miyako and Kuwagasaki merged on April 1, 1924. On March 3, 1933, much of the town was destroyed by the 1933 Sanriku earthquake, which killed 911 people and destroyed over 98% of the buildings in the town. Miyako attained city status on June 20, 1940.
On June 6, 2005, Miyako absorbed the town of Tarō, and village of Niisato, more than doubling the old city's size. On January 1, 2010, Miyaki absorbed the village of Kawai (also from Shimohei District).
On March 11, 2011, Miyako was devastated by a tsunami caused by the 2011 Tōhoku earthquake. Only about 30–60 boats survived from the town's 960 ship fishing fleet. A subsequent field study by the University of Tokyo's Earthquake Research Institute revealed that the waters had reached at least 37.9 metres (124 ft) above sea level, almost equaling the 38.2 metres (125 ft) meter record of the 1896 Sanriku earthquake tsunami. The final reported death toll from the disaster was 420 confirmed dead, 92 missing, and 4005 buildings destroyed.
Some of the most iconic footage of the tsunami, repeatedly broadcast worldwide, was shot in Miyako. It shows a dark black wave cresting and overflowing a floodwall and tossing cars, followed by a fishing ship capsizing as it hit the submerged floodwall and then crushed as it was forced beneath a bridge.
Miyako has a mayor-council form of government with a directly elected mayor and a unicameral city legislature of 28 members.
The local economy of Miyako is based heavily on commercial fishing and food processing.