The Odakyu Electric Railway Company, Ltd. (小田急電鉄株式会社, Odakyū Dentetsu kabushiki gaisha), commonly known as Odakyū or Odawara Kyuko, is a major railway company based in Tokyo, Japan, best known for its Romancecar series of limited express trains from Tokyo to Odawara, Enoshima, Tama New Town, and Hakone.

Unlike the Odawara line, rarely were pre-World War II Japanese private railways constructed with double-track and fully electrified from the first day of operation.

The abbreviation Odakyu was made popular by the title song of the 1929 movie Tōkyō kōshinkyoku and eventually became the official name of the railroad on March 1, 1941.

After the 1950s, due to rapid Japanese economic growth, Odakyu was faced with an explosive increase of population along with its lines.

Commuter passengers had to use very crowded trains every morning, and complained strongly with the delay of improvements from the railway company.

All of its lines are double- or quadruple-tracked within Tokyo Metropolis as of March 2018, a project first decided in December 1964 but due to NIMBY land acquisition difficulties, complex and expensive workarounds were constructed and finished, taking a half century.

The Romancecar 3000 series "SE" was tested at speeds of up to 145 km/h (90 mph) in 1957, achieving a world record for narrow-gauge 1,067 mm (3 ft 6 in) lines at the time.

(As of March 17, 2018 timetable revision) Romancecar limited express services require a supplementary surcharge.