Shamrock is a city in Wheeler County, Texas, United States. As of the 2020 census, the city had a total population of 1,789. The city is located in the eastern portion of the Texas Panhandle, centered along the crossroads of Interstate 40 (formerly U.S. Route 66) and U.S. Route 83. Due to its location at this intersection, Shamrock has been called the gateway to the Southwest. It is 110 miles (180 km) east of Amarillo, 188 miles (303 km) west of Oklahoma City, and 291 miles (468 km) northwest of Dallas.

Located in south-central Wheeler County, Shamrock was the largest town in the county in the late 19th century. George and Dora Nickel consented to keep the first post office in their dugout in 1890. The mail was to be carried once a week from Mobeetie. The neighbors decided to let George name the office. His Irish-American mother had told him always to depend on a shamrock to bring him good luck, so holding true to his Irish descent, he suggested "Shamrock" for the name of the office. When a mysterious fire destroyed his dugout, however, George Nickel's post office never opened. Mary Ruth Jones became Shamrock's first postmistress, running the Shamrock post office out of the Jones family home.

In 1902, the Chicago, Rock Island and Gulf Railway set up a station in the town, calling it "Wheeler" like the county, but later changing it back to the original name of Shamrock in 1903, which prompted the reopening of the Shamrock post office. By 1907, the town was competing with the towns of Story and Benonine as trade centers.

The town continued its growth as other businesses moved into the city, including the county newspaper, which moved from Story and renamed itself from the Wheeler County Texan to the Shamrock Texan, several banks, and Shamrock Cotton Oil Mill. In 1911, E. L. Woodley became the mayor of the newly incorporated city. In 1926, the discovery of oil and the operation of natural gas wells by Shamrock Gas Company helped spur the city's continuing growth. A decline in the oil industry caused the population to drop in the 1940s, but it rebounded in the next decade with the improvement of Route 66. By the 1980s, the town was home to an established modern school system, a chemical plant, oil and gas processing plants, and a hospital.

At its peak in 1930, Shamrock had a population of 3,778. Despite some rebounds, the city population continues to fluctuate. According to the 2020 census, the city population has dropped to its second-lowest recorded point with 1,789 residents. Despite this, Shamrock remains the second-largest city on the Texas segment of Route 66, after Amarillo.

According to the United States Census Bureau, the city has a total area of 2.1 square miles (5.4 km²), all land.

As of the 2020 census, Shamrock had a population of 1,789. The median age was 38.9 years, 26.8% of residents were under the age of 18, and 20.4% of residents were 65 years of age or older. For every 100 females there were 100.1 males, and for every 100 females age 18 and over there were 92.1 males age 18 and over.

0.0% of residents lived in urban areas, while 100.0% lived in rural areas.