The A4000, or Commodore Amiga 4000, was the successor of the A2000 and A3000 computers. The machine came in two models, the A4000/030 and the A4000/040, with a Motorola 68EC030 or Motorola 68040 CPU, respectively.

The A4000 originally came in a white desktop box with a separate keyboard.
There was also a tower version called the A4000T, produced in small numbers.

Features of the desktop version:

• 2x front accessible 3½ inch drive bays.
• 1x front accessible 5¼ inch drive bay.
• 1x high density 3½ inch floppy disk drive.
• 2x internal 3½ inch drive mountings.
• AGA chipset.
• IDE disk interface.

Interestingly, unlike most other Amigas, early A4000 machines had the CPU mounted in a daughterboard using a special CPU slot. The mainboard had no CPU at all. Later machines had the CPU surface mounted on the mainboard in an effort to reduce costs.

The tower version was the only Amiga ever to have both SCSI and IDE interfaces built-in on the motherboard. Having driver software for both interfaces on the ROM meant that some other parts of AmigaOS had to be moved from the ROM, and thus the A4000T is the only machine to have the file "workbench.library" stored on disk. It was also the only Amiga to use a PC form factor for the motherboard, and the first (and only) to use a Lithium Ion backup battery instead of a NiCd. This backup battery is also one of the most common causes of problems in the aging A4000s: it has a tendency to eventually leak. The released fluids are somewhat corrosive and can eventually damage the motherboard.

This was the final "big-box" machine to be put out by Commodore International. Only a couple hundred 4000T's were produced before the whole company folded. Production of the 4000T's was restarted after ESCOM bought the Amiga assets. The ESCOM-manufactured 4000T's had minor differences with the old one, including the substitution of the high density floppy drive with a double density one..

The A4000 designation was also used on an Acorn Archimedes model.

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