Inline skates are boots with wheels arranged in a single line from front to back, allowing one to move in an ice skate-like fashion. Inline skates are technically a type of roller skate, but most people associate the term roller skates with quad skates, another type of roller skate with a two-by-two wheel arrangement similar to a car. Quad skates were popularized in the late 19th and early 20th centuries. Inline skates became prominent in the late 1980s with the rise of Rollerblade, Inc., and peaked in the late 1990s. The registered trademark Rollerblade has since become a generic trademark: "rollerblading" is now a verb for skating with inline skates, or "rollerblades."

In the 21st century, inline skates come in many varieties, suitable for different types of inline skating activities and sports such as recreational skating, urban skating, roller hockey, street hockey, speed skating, slalom skating, aggressive skating, vert skating, and artistic inline skating. Inline skaters can be found at traditional roller rinks, street hockey rinks, skateparks, and on urban streets. In cities around the world, skaters organize urban group skates. Paris Friday Night Fever Skate (Randonnée du Vendredi Soir) is renowned for its large crowd size, as well as its iconic +10 mile urban routes. Wednesday Night Skate NYC is its equivalent in New York City, also run by volunteers, albeit smaller in size.

The documented history of inline skates dates back to the early 18th century, when enterprising inventors sought to make boots roll on wheels to emulate the gliding of ice blades on dry land. Because these wheeled skates were modeled after ice blades, their wheels were arranged in a single line. Skates were simply assumed to have a single runner, whether it was a steel blade on an ice skate or a row of wheels on a wheeled skate.

The first patented wheeled skate was filed in France in 1819 by Charles-Louis Petibled. From that point forward, more patents and documented designs continued to explore wheeled alternatives to ice skates. Around 1860, wheeled skates began to gain popularity, and new patents appeared under names such as "roller-skates" and "parlor skates". As inventions increased, roller skates began to diverge from the original single-line layout. Inventors experimented with two rows of wheels as a learning platform for beginner skaters. These double-row skates offered greater stability, but they were difficult to turn.

In 1863, James Plimpton invented a roller skate with four wheels arranged in a two-by-two configuration, similar to a wagon, and added a clever mechanism for turning. It was the first double-row skate that allowed beginners to steer easily by simply leaning in the desired direction. Plimpton's invention sparked a rapid rise in roller skate popularity and spread across both sides of the Atlantic, creating a period of "rinkomania" during the 1860s and 1870s. His design also redefined the term "roller skate", which no longer referred to all wheeled skates but became synonymous with the "two-by-two" Plimpton style.

The development of precision ball bearings in the mid-19th century helped make bicycles more efficient and practical. By the 1880s, Plimpton-style roller skates similarly incorporated ball bearings into their wheel assemblies, making skates roll more efficiently. At the same time, manufacturers began operating skating rinks as promotional ventures from the 1880s through the 1910s. All of these further fueled the Plimpton skate craze.

Although Plimpton's roller skates took center stage, inventors and enterprises continued to introduce new roller skates with a single line of wheels between the 1870s and the 1910s. These models included features such as brakes, pneumatic tires, and foot stands placed below the center of the wheels.

From the 1910s through the 1970s, many new variations of single-line wheeled skates were patented and manufactured. While still in the shadow of 2x2 roller skates, some models began to gain popularity among ice hockey players by the 1960s and 1970s, due to their better emulation of ice blades. In particular, off-season training skates used by USSR speed skaters inspired Gordon Ware of the Chicago Roller Skate Company to develop and patent a wheeled skate, which was sold through Montgomery Ward in 1965 under the name "Roller-Blade". In 1973, Ralph Backstrom promoted the Super Sport Skate, a joint venture with his friend Maury Silver, as an off-season training tool for hockey players. Both of these skate models became direct precursors to modern inline skates.