A V engine, or Vee engine is a common configuration for an internal combustion engine. The cylinders and pistons are aligned, in two separate planes or 'banks', so that they appear to be in a "V" when viewed along the axis of the crankshaft. The Vee configuration generally reduces the overall engine length, height and weight compared to an equivalent inline configuration.

In 1896, Karl Benz patented his design for the first internal combustion engine with horizontally opposed pistons. Usually, each pair of corresponding pistons from each bank of cylinders share one crank pin on the crankshaft, either by master/slave rods or by two ordinary connecting rods side by side. Some authorities even regard this as a distinguishing feature of a true Vee engine, and for example divide flat engines into boxer engines which do not share crank pins in this way, and 180° engines which do. On the other hand, some important V-twin engine designs have two-pin cranks. However, in German, these engines are all identified as boxermotors. (that is wrong, the German terminology distinguishes the "true" Boxer and 180° bank angle engines as such)

Various cylinder bank angles of Vee are used in different engines; depending on the number of cylinders, there may be angles that work better than others for stability. Very narrow angles of Vee combine some of the advantages of the Vee engine and the straight engine (primarily in the form ofcompactness) as well as disadvantages; the concept is an old one pioneered by Lancia, but recently reworked by Volkswagen Group.

Some Vee configurations are well-balanced and smooth, while others are less smoothly running than their equivalent straight counterparts. With an optimal angle, V16s have even firing order and exceptional balance. The V10 and crossplane V8 engine can be balanced with counterweights on the crankshaft. V12s, being in effect two straight-6 engines married together, always have even firing and exceptional balance regardless of angle. Others, such as the V2, V4, V6, flatplane V8, and V10, show increased vibration and generally require balance shafts.

Certain types of Vee engine have been built as inverted engines, most commonly for aircraft. Advantages include better visibility in a single-engined airplane, and lower centre of gravity. Examples include World War II German engines produced by Daimler-Benz and Jumo.

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

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