The Honda CBR400 is a Japanese domestic market small-capacity sport motorcycle, part of the CBR series introduced by Honda in 1983. It is the first Honda motorcycle to wear a CBR badge.

The CBR400R (NC17 ) naked bike was launched in December 1983. The 4-valves per cylinder, air-cooled, four-stroke, DOHC, inline-four engine had a rotational-speed valve stop mechanism "REV" (a prototype of Honda's VTEC system) that changed from two valves into four valves at 9,500 rpm.{{cn|date=September 2017}} The following two years, it came as semi- and fully faired version as the F3 Endurance.{{cn|date=September 2017}} The CBR400R and early CBR400RR models both carry the model number NC23, which makes up the first part of these bikes' frame numbers.{{cn|date=September 2017}} In 1986 the CBR400R was also known as Aero, Jellymould, as it shares its major design features with the rest of the early CBR600F and CBR1000F Hurricane family of motorcycles,^[3] which included significantly rounded body shapes. whereas the later 1988 model was designated CBR400RR and was also known as the Tri-Arm,^[3] after its racing inspired braced swingarm.{{cn|date=September 2017}}

The CBR400RR in 1992 was referred to as the ‘Baby Blade’ replica, then in 1994 it was styled to closely look like the CBR900RR or Fireblade motorcycle.^[1] though over the years, in performance and handling it was more closely compared to the CBR600.^[1] The CBR400RR preceded the {{convert|900|cc|abbr=on}} Fireblade by four model years, going through one major rework (signified by a new "gull-arm" swing arm design.

The CBR400RR models are the NC23 and NC29 CBR400RR-J (1988), CBR400RR-K (1989), CBR400RR-L (1990–1991), CBR400RR-N (1992–1993) and CBR400RR-R (1994).^[2] The name "Tri-Arm" is shown on the CBR400RR-J's bodywork, along with Hurricane, but the CBR400RR-K dropped the latter designation.^[3]

The NC23 CBR400RR features a standard extruded beam frame, the rear of the seat unit slopes forwards, and the seat unit subframe is totally separate from the main chassis of the bike. The NC23 & NC29 (only the -R models of which carry the FireBlade name) had several modifications to the frame.{{cn|date=September 2017}} The main rails were of a 'cranked' design, the seat support structure had a larger rail that was welded to the frame, the rear of the tail section now had a slight recurve to it, and the swingarm was given a gull-wing shape on one side to give ground clearance for the exhaust link pipe.{{cn|date=September 2017}}

In 1985, Honda brought a CBR400F to the US for testing, on which Cycle World recorded a {{cvt|0|to|1/4|mi}} time of 13.63 seconds at {{cvt|95.94|mph}} and a top speed of {{cvt|111|mph|order=flip}}.

In 2013, Honda released the new twin-cylinder CBR400R along with its naked model, the CB400F (not to be confused with four-cylinder CB400 Super Four), and sport adventure model, the CB400X, which is based on the CBR500R, CB500F, and CB500X respectively. These models are sold in Japan & Singapore only.^[4]

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