The Colt Walker was a single-action revolver with a revolving cylinder holding six charges of black powder behind six bullets (typically .44 caliber lead balls). It was designed in 1847 as a collaboration between Captain Samuel Hamilton Walker and American firearms inventor Samuel Colt.

The 1847 Colt Walker was the largest and most powerful black powder repeating handgun ever made. It was created in the mid-1840s in a collaboration between Texas Ranger Captain Samuel Hamilton Walker (1817–47) and American firearms inventor Samuel Colt (1814–62), building upon the earlier Colt Paterson design. Walker wanted a handgun that was extremely powerful at close range.

Samuel Walker carried two of his namesake revolvers in the Mexican–American War. He was killed in battle the same year his famous handgun was invented, 1847, shortly after he had received them. Only 1100 of these guns were originally made, which makes originals extremely rare and expensive to acquire. On October 9, 2008, one specimen that had been handed down from a Mexican War veteran sold at auction for US$920,000.

The Republic of Texas had been the major purchaser of the early Paterson Holster Pistol (No. 5 model), a five shot cal .36 revolver, and Samuel Walker became familiar with it during his service as a Texas Ranger. In 1847, Walker was engaged in the Mexican-American War as a captain in the United States Mounted Rifles. He approached Colt, requesting a large revolver to replace the single-shot Aston Johnson holster pistols then in use. The desired .44-.45 caliber revolver would be carried in saddle mounted holsters and would be large enough to dispatch horses as well as enemy soldiers. The Colt Walker was used in the Mexican-American War and on the Texas frontier.

Medical officer John “Rip” Ford took a special interest in the Walkers when they arrived at Veracruz. He obtained two examples for himself and is the primary source for information about their performance during the war and afterward. His observation that the revolver would carry as far and strike with the same or greater force than the .54 caliber Mississippi Rifle seems to have been based on a single observation of a Mexican soldier hit at a distance of well over one hundred yards. The Walker, unlike most succeeding martial pistols and revolvers, was a practical weapon out to about 100 yards.

The Colt Walker holds a powder charge of 60 grains (3.9 g) in each chamber, more than twice what a typical black powder revolver holds. It weighs 4 12pounds (2 kg) unloaded, has a 9-inch (230 mm) barrel, and fires a .44 caliber (0.454 in (11.5 mm) diameter) conical and round ball. The initial contract called for 1,000 of the revolvers and accoutrements. Colt commissioned Eli Whitney Junior to fill the contract and produced an extra 100 revolvers for private sales and promotional gifts.

In addition to its large size and weight, problems with the Walker included ruptured cylinders after firing. This has been attributed to primitive metallurgy, soldiers allowing powder to spill across the mouths of the chambers, and even loading the original conical bullets backwards into the chambers. Under 300 of the original 1,000 were returned for repair due to a ruptured cylinder. Lard was loaded into the mouths of the cylinders on top of each bullet after loading to prevent the spark from igniting all chambers at once, a practice which continues to this day among black-powder revolver shooters, and although each chamber held 60 grains of Powder, Colt recommended no more than 50 grains in each.

The Walker had an inadequate loading lever catch that often allowed the loading lever to drop during recoil, preventing fast follow-up shots. Period-correct fixes for this often included placing a rawhide loop around both the barrel and loading lever, to prevent the loading lever from dropping under recoil and locking the action.