4-6-4-4

{{Short description|Duplex locomotive wheel arrangement}}

{{One source|date=May 2025}}

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| image1 = WheelArrangement 4-6-4-4.svg

| caption1 = 4-6-4-4 wheel arrangement

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| caption2 = The PRR Q1 6130 - the only locomotive with this wheel arrangement

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In Whyte notation, a 4-6-4-4{{cite web |title=4-4-4-4, 6-4-4-6, etc. "Duplex Drive" Locomotives in the USA |url=https://www.steamlocomotive.com/locobase.php?country=USA&wheel=Duplex |website=steamlocomotive.com |access-date=20 May 2025}} is a railroad steam locomotive that has four leading wheels followed by six coupled driving wheels, a second set of four driving wheels and four trailing wheels.

Other equivalent classifications are:

• UIC classification (also known as German or Italian classification): 2CB2
• French classification: 2322
• Turkish classification: 3524
• Swiss classification: 3/5+2/4 up to the early 1920s, later 5/9

The sole example of this arrangement was the PRR Q1. This locomotive was essentially a prototype in the development of the PRR Q2, a 4-4-6-4.