Engine configuration is an engineering term that refers to the layout of pistons in an internal combustion engine. The term block is often interchangeable with engine in this terminology, it's common to see the term V block and V engine, both referring to the same thing.

The most common forms are all based on a single engine block and crank case that are milled from a single piece of cast metal, with the pistons running in a row. These types of engines are all inline engine designs, which can be further broken down by the configuration of the cylinder rows, or banks. In the straight design all of the pistons are placed in a single row, whereas in the V configuration they are split into two banks sharing a single crank case. The horizontally opposed (or flat) design is essentially a V-block with the cylinder banks at 180 degrees from each other, as opposed to 60 or so for the V. H, W, square, opposed piston and delta designs with more than one bank and crankcase have also seen limited use. An extremely odd configuration is the U engine, which is actually two separate straight engines with crankshafts linked by a central gear.

Another grouping, used almost entirely in aircraft, are the radial and rotary designs. In both cases the pistons are placed in individual cylinders arranged around a central crankcase like spokes on a wheel. This configurations keeps all of the cylinders at the front of the engine, which makes it easy to cool with airflow alone.

A final common configuration actually refers to the engine as a whole, in the Wankel engine where the "piston" spins instead of reciprocating. Although ostensibly not an engine configuration, it is often mentioned in this context anyway.