Design work on the new pistol began in the early 1990s and the final product known as the M9 (adapted to fire the 9×19mm Parabellum cartridge) was officially unveiled in the spring of 1999.

These pistols were developed primarily for concealed carry and have a shortened barrel, slide, smaller frame and a reduced magazine capacity.

[3][better source needed] The frame is an injection-molded synthetic polymer[2] and parts of the trigger and striker mechanisms are pressed from sheet metal.

[4] The Steyr M series uses a very high grip profile which holds the barrel axis close to the shooter's hand and makes the Steyr M more comfortable to shoot by reducing muzzle rise and allowing for faster aim recovery in rapid shooting sequence.

[5] The Steyr M series of pistols employs the mechanically locked Browning short recoil method of operation with a linkless, vertically dropping barrel.

The pistols are fed using a detachable steel magazine of the single position feed type with the cartridges arranged in a staggered column pattern.

[5] These safeties enable safe handling of the pistol with a round present in the chamber (the so-called "cocked and locked" condition) and allow for rapid deployment and immediate firing; this arrangement however does not permit the firing mechanism to be re-cocked in case of a misfire after the trigger has been pulled.

[4] Other safety features include a loaded chamber indicator and an integrated limited access lock operated using a key to prevent unauthorized use.

[4] When pushed in and rotated to the "S" position with the provided key, the lock disables the trigger and barrel and prevents the pistol from being disassembled.

Optional adjustable or non-adjustable tritium-illuminated three-dot low light situation sights can also be fitted to the Steyr M; these have a conventional rectangular profile.

The original pistol's frame also has proprietary mounting rails for attaching accessories, such as a tactical light or laser pointer.

The Steyr Arms "target" logo is also in the center of both sides of the grip, and there is a single finger groove on the front strap.

The first generation models are the only guns in the series that have a rounded trigger guard, somewhat resembling the Smith & Wesson SW.

Other features include enhanced finger grooves, stippling on the front and back straps, a straightened trigger guard, thumb rests and a single-slot 2324 Picatinny accessory rail.

Second generation models also incorporated Steyr's target insignia with "Mannlicher" molded into the left side of the grip to signify the company.

In 2009, Steyr stopped importing the second generation line, citing economic fluctuation that meant they were unable to price the guns competitively.

The first was introduced in 2010 and designated the C-A1 (for "Compact"), which combined the longer M-sized grip and the shorter S-sized slide and barrel.

In 1999, Wilhelm Bubits and Friedrich Aigner, the designers of the original Steyr M, filed the first ever patent for a modular handgun.

[9] However it was not until the fourth generation models where Steyr offered a fully removable serialized firing control unit.

Internally, the design is largely the same, but the ejector was modified to counteract erratic spent cartridge case ejection.