Sturm, Ruger & Co., Inc., better known by the shortened name Ruger, is an American firearm manufacturing company based in Southport, Connecticut with production facilities also in Newport, New Hampshire, Mayodan, North Carolina and Prescott, Arizona. The company was founded in 1949 by Alexander McCormick Sturm and William B. Ruger and has been publicly traded since 1969.

Ruger produces bolt-action, semi-automatic, and single-shot rifles, shotguns, semi-automatic pistols, and single- and double-action revolvers. According to the ATF statistics for 2015, Ruger is currently America's largest firearm manufacturer, as well as the second largest pistol/revolver manufacturer (behind Smith & Wesson) and rifle manufacturer (behind Remington) in the United States.

Sturm, Ruger & Company was founded by William B. Ruger and Alexander McCormick Sturm in 1949 in a small rented machine shop in Southport, Connecticut.

Just prior to their partnership, Bill Ruger had successfully duplicated two Japanese "baby" Nambu pistols in his garage, from a captured Nambu that he acquired from a returning Marine, at the close of World War II. When it came to designing their first semi-auto pistol, Ruger decided to incorporate the looks of the German 9mm Luger and the American Colt Woodsman into their first commercially produced .22 caliber pistol (see Ruger Standard), which became so successful that it launched the entire company.

Ruger is a dominant manufacturer in the .22 LR rimfire rifle market in the U.S., due primarily to the sales of its Ruger 10/22 semiautomatic rifle. The 10/22 is very popular due to being relatively inexpensive and of good quality. As a result, a wealth of after-market accessories and parts were made available for it, which has further increased its popularity. The availability and variety of after-market parts makes it possible to build a 10/22 using only these parts; most of which are marketed to target shooters and hunters.

Ruger similarly dominates the .22 rimfire semi-automatic pistol market with the Ruger MK II and Ruger MK III, descendants of the Ruger Standard pistol. Like the 10/22, the MkII is supported with a wide variety of after-market accessories. The 22/45 is similar to the Ruger Standard family of pistols but features a different grip angle, that of the Colt 1911 (as opposed to that of a Luger utilized in the Ruger Standard).

Ruger Casting has plants in Newport, New Hampshire and Prescott, Arizona, making ferrous, ductile iron and commercial titanium castings. Ruger Golf makes steel and titanium castings for golf clubs made by a number of different brands.

Sturm, Ruger stock has been publicly traded since 1969, and became a New York Stock Exchange company in 1990 (NYSE:RGR). After Alex Sturm’s death in 1951, William B. Ruger continued to direct the company until his death in 2002.

From 1949 through 2004, Ruger manufactured over 20 million firearms, and currently offers models for hunting, target shooting, self-defense, collecting, and law enforcement.

Sturm, Ruger & Co. is headquartered in Southport, Connecticut, and maintains manufacturing facilities in Newport, New Hampshire, Prescott, Arizona, and Mayodan, North Carolina. Ruger's subsidiaries are Ruger Precision Metals LLC in Earth City, Missouri, Pine Tree Castings in Newport, New Hampshire, and Ruger Sportswear & Accessories in Mayodan, North Carolina.

Of the total 2,288 makers of civilian firearms operating in the United States from 1986–2010, Ruger led the industry with 15.3 million firearms produced within the period. Ruger was ranked the number one U.S. firearms manufacturer from 2008–2011. In 2011, Ruger manufactured 1,114,687 firearms, as their promotion, the "Million Gun Challenge to Benefit the NRA", played a significant role in the company maintaining its top U.S. manufacturer status. The company has set a new goal of 2 million firearms produced per year. From 2009 to 2012, Ruger was the top-seller of handguns.

Ruger breaks down their products into nine categories: bolt-action rifles, single-shot rifles, autoloading rifles, lever-action rifles, shotguns, centerfire pistols, rimfire pistols, double-action revolvers, and single-action revolvers.

Sturm, Ruger & Co. has a history of assisting USA Shooting in direct funds contribution, and by creating Distributor Exclusive models through TALO Distributors, Inc.

On August 3, 2010, in Manchester, Connecticut, Omar Thornton, a disgruntled employee who had been fired for stealing, murdered nine coworkers at the Hartford Beer Distributor, using a Ruger 9 mm handgun.

On November 5, 2017, at the First Baptist Church in Sutherland Springs, Texas, Devin Kelley, who had been confined one year for a domestic violence conviction, murdered 26 praying churchgoers, using a Ruger AR-556.