公路自行车，俗称“公路车”或“自行车赛车”。是在平滑的公路路面上使用的自行车车种，可用于公路自行车竞赛。为了使骑行达到高速，车身重量较轻且风阻较小。

由于上述的特点，公路单车的骑行速度要比普通单车快很多。普通的爱好者稍加训练以后，一般都可以达到一小时骑35公里平路的水准。而一个优秀的公路单车运动员在路况良好的平地路段上长距离骑行时的平均时速可以保持在每小时40至50公里。

A racing bicycle, also known as a road bike, is a bicycle designed for competitive road cycling, a sport governed by according to the rules of the Union Cycliste Internationale (UCI). The UCI rules were altered in 1934 to exclude recumbent bicycles.

The most important characteristics about a racing bicycle are its weight and stiffness which determine the efficiency at which the power from a rider's pedal strokes can be transferred to the drive-train and subsequently to its wheels. To this effect racing bicycles may sacrifice comfort for speed. The drop handlebars are positioned lower than the saddle in order to put the rider in a more aerodynamic posture. The front and back wheels are close together so the bicycle has quick handling. The derailleur gear ratios are closely spaced so that the rider can pedal at their optimum cadence. Other racing bicycles, especially those used in time trialling, prioritize aerodynamics over comfort.