A V engine is a common configuration for an internal combustion engine in which the pistons are aligned so that, if viewed along the line of the crankshaft, they appear to be in a V. The V configuration reduces the overall engine length and weight compared to an equivalent straight engine.

Some V configurations are well-balanced and smooth, while others are less smoothly running than their equivalent straight counterparts. Some designs, such as the V8, V12 and V16 are smooth running and balanced, while others, such as the V2, V4, V6 and V10 show increased vibration and generally require external balancing shafts. Some exceptions occur with certain crankshaft configurations. Various angles of V are used in different engines; depending on the number of cylinders, there may be angles that work better than others for stability.

It is common for V engines to be described with V# notation, where # is how many cylinders it has: