Edo (), also romanized as Jedo, Yedo or Yeddo, is the former name of Tokyo.
Edo, formerly a jōkamachi (castle town) centered on Edo Castle located in Musashi Province, became the de facto capital of Japan from 1603 as the seat of the Tokugawa shogunate. Edo grew to become one of the largest cities in the world under the Tokugawa.
After the Meiji Restoration in 1868 the Meiji government renamed Edo as Tokyo (, "Eastern Capital") and relocated the Emperor from the historic capital of Kyoto to the city. The era of Tokugawa rule in Japan from 1603 to 1868 is known as the Edo period.
Before the 10th century, there is no mention of Edo in historical records, but for a few settlements in the area. Edo first appears in the Azuma Kagami chronicles, that name for the area being probably used since the second half of the Heian period. Its development started in late 11th century with a branch of the Kanmu-Taira clan called the Chichibu clan, coming from the banks of the then-Iruma River, present day upstream of Arakawa river. A descendant of the head of the Chichibu clan settled in the area and took the name Edo Shigetsugu, likely based on the name used for the place, and founded the Edo clan. Shigetsugu built a fortified residence, probably around the tip of the Musashino terrace, which would become the Edo castle. Shigetsugu's son, Edo Shigenaga, took the Taira's side against Minamoto no Yoritomo in 1180 but eventually surrendered to Minamoto and became a gokenin for the Kamakura shogunate. At the fall of the shogunate in the 14th century, the Edo clan took the side of the Southern court, and its influence declined during the Muromachi period.
In 1456, a vassal of the Ōgigayatsu branch of the Uesugi clan, started to build a castle on the former fortified residence of the Edo clan and took the name Ōta Dōkan. Dōkan lived in this castle until his assassination in 1486.