Yao is a city located in Osaka Prefecture, Japan. As of 31 January 2022, the city had an estimated population of 263,436 in 126509 households and a population density of 6300 persons per km2. The total area of the city is 41.72 square kilometres (16.11 sq mi). The city is the birthplace of the Kawachi ondo style of folk singing.

The Osaka Metro Tanimachi Line is a rapid transit line of Osaka Metro, running from Dainichi Station in Moriguchi to Yaominami Station in Yao through Osaka. Despite chronologically being the system's fourth line, its official name is Rapid Electric Tramway Line No. 2 (高速電気軌道第2号線), while the Osaka Municipal Transportation Bureau refers to it as Osaka City Rapid Railway Line No. 2 (大阪市高速鉄道第2号線), and in MLIT publications, it is written as Line No. 2 . On line maps, stations on the Tanimachi Line are indicated with the letter T.