The is an electric multiple unit (EMU) train type in Japan, operated by the private railway operator Keio Corporation since 2001 on the Keio Line and its branches in Tokyo and Kanagawa Prefecture.
The 9000 series 8-car sets are used mainly on the Keio Line, the Takao Line, and the Sagamihara Line. These sets are mainly used on Local services during daytime. They are also used on 10-car Special Express and Rapid trains. Sets are coupled to 2-car Keio 7000 series sets to form 10-car trains.
The 9030 series 10-car sets are used primarily on inter-running services to and from the Toei Shinjuku Line.
The front end design is based on the design of the Keio 5000 series. The body is made of stainless steel. While most of the sets were built at Nippon Sharyo, some were built at Tokyu Car Corporation. The front portion is made of steel painted ivory white.
The 9030 series sets differ from the earlier 8-car sets in having UV-cutting glass for the wide windows, eliminating the need for roller blinds, and having full-colour LED destination indicator panels.
As of 1 April 2013, the fleet consists of eight 8-car 9000 series sets and twenty 10-car 9030 series sets.
The 8-car 9000 series sets (9701 to 9708) are formed as shown below, with four motored (M) cars and four non-powered trailer (T) cars, and with car 1 at the western end.
The 10-car 9030 series sets (9730 to 9749) are formed as shown below, with five motored (M) cars and five non-powered trailer (T) cars, and with car 1 at the western end.
Passenger accommodation consists of longitudinal bench seating throughout. Priority seats are provided at the end of each car.
From 1 November 2018, 9000 series set 9731 was wrapped in a pink livery incorporating several Sanrio characters, such as Hello Kitty. It carried this livery until August 2024.
Following its refurbishment, set 9731 received a new Sanrio livery only applied to its front ends. Keio states that it has discussed adorning other refurbished sets to distinguish them from unrefurbished sets.
On 7 February 2025, Keio announced that its 10-car 9000 series fleet would undergo a programme of refurbishment. The work includes a renovated interior incorporating some design elements of the then-to-be-introduced 2000 series, with additional stanchion poles, dimpled stanchion poles in priority seating areas for improved grip, and wheelchair- and stroller-accessible "free spaces" in all cars. Treated sets also feature a more efficient, full SiC (silicon carbide)-based traction system, which Keio states offers approximately 20% energy savings over the type's original traction system and approximately 70% energy savings over train types without VVVF (variable frequency) traction control.
Refurbished sets returned to service from 10 March 2025.