The Tobu 50000 series (東武50000系, Tōbu 50000-kei) is a DC electric multiple unit (EMU) commuter train type operated by the private railway operator Tobu Railway in Japan since March 2005, manufactured by Hitachi to its "A-train" concept. The trains represent the first use of aluminium body cars on Tobu commuter trains. They are also the first Tobu trains to feature bilingual (Japanese and English) automated passenger announcements.

• 50000 series: 9 x 10-car sets introduced from March 2005 on the Tobu Tojo Line and from September 2020 on the Tobu Skytree Line inter-running services
• 50050 series: 18 x 10-car sets introduced from March 2006 on Tobu Skytree Line inter-running services
• 50070 series: 7 x 10-car sets introduced from July 2007 on Tobu Tojo Line inter-running services
• 50090 series: 6 x 10-car sets with variable seat configurations introduced from June 2008 on Tobu Tojo Line TJ Liner services

The first 50000 series set, 51001, was delivered in November 2004 and entered service on the Tobu Tojo Line on 16 March 2005, followed by second-batch set 51002 in October 2005. The second set differs in having an emergency door in the front ends, and externally resembles the 50050 series used on the Tobu Skytree Line (see below).^[1]

Two more sets, 51003 and 51004, were delivered during fiscal 2009.^[2] 51003 was delivered to Shinrinkōen Depot in January 2010,^[3] followed by 51004 in February 2010.^[4] These two sets have pairs of opening windows and interiors based on sets 51061 onward.

• Set 51001 with no front-end doors in December 2019
• Set 51009 with modified side windows including opening sections in December 2019

Total number of vehicles built: 90

The 10-car 50050 series sets were built for use on the Tobu Isesaki, Skytree and Nikko lines, and inter-running services through the Tokyo Metro Hanzomon Line to the Tokyu Den-en-toshi Line displacing the earlier 30000 series sets.^[5]

The first set (51051) entered service on 18 March 2006, and as of January 2007, 10 sets were in service. While broadly based on the Tojo Line 50000 series design with emergency end doors, cars are 30 mm (1.2 in) narrower (2,770 mm (9 ft 1 in) compared with 2,800 mm (9 ft 2 in)) to cope with reduced clearances on the subway lines.

Sets 51061 onward have different seat covers and pairs of opening windows (like the 50090 series) instead of the large single-pane sealed windows on earlier units.

Three more sets (51066 to 51068) were delivered during fiscal 2009.^[2]

From October 2012, set 51052 was modified with opening panes in four side windows per car, in the same style as Tojo Line set 51075 and JR East 209 series sets.^[6]

Total number of vehicles built: 180

The 10-car 50070 series sets were built for use on Tobu Tojo Line and Tokyo Metro Yūrakuchō Line inter-running services, and also on Tokyo Metro Fukutoshin Line inter-running services from June 2008.^[7]

The first set (51071) was delivered in early March 2007, entering revenue-earning service in July. It differs from earlier variants in having full-colour LED destination indicators, and is also equipped with ATO for subway operation.

A total of four sets were delivered by March 2008.^[8]

A fifth set, 51075, was delivered in August 2008.^[9] This set differs in having opening windows similar in design to those added to JR East 209 series EMUs.^[6]

A further two sets, 51076 and 51077, were delivered during fiscal 2011, with 51076 delivered in November 2011,^[10] and 51077 in January 2012.^[11] These sets differ in having 17" LCD displays above every door, instead of the LED dot-matrix displays used on earlier sets, and also have pairs of opening side windows instead of the large single panes.

Total number of vehicles built: 70

Four 10-car 50090 sets were delivered in February and March 2008 for use on new Tobu Tojo Line limited-stop evening TJ Liner services starting from the start of the new timetable on 14 June 2008.^[12] Internally, these trains feature rotating seats that can be arranged longitudinally for daytime services and in forward-facing transverse pairs for "Liner" services. These trains are also used on up "Rapid Express" services in the late afternoon and night as well as the newly introduced Kawagoe Limited Express services from 16 March 2019. Externally, the sets feature a blue waistline stripe running the length of each car, with a "TOJO LINE" logo.^[13]

A public preview run of the 50090 series took place on 23 March 2008 from Ikebukuro to Shinrinkōen station, followed by a photographic event at Shinrinkōen depot.^[14]

A fifth set, 51095, was delivered from Hitachi in September 2010,^[15] followed by 51096 in November 2010, in preparation for an increase in the number of TJ Liner services from the start of the revised timetable on 5 March 2011.^[16]

Total number of vehicles built: 60

• Seibu 40000 series, a Seibu Railway commuter EMU type that also features rotating longitudinal/transverse seating
• Keio 5000 series, a Keio commuter EMU type that also features rotating longitudinal/transverse seating
• Keikyu 2100 series, a Keikyu commuter EMU type also features transverse seating
• Keikyu N1000 series, another Keikyu commuter EMU type also features rotating transverse seating (batch 20 only)