The Buick V8 is a family of V8 engines produced by the Buick division of General Motors (GM) between 1953 and 1981. All were 90° water-cooled V8 OHV naturally aspirated engines.

Buick had produced only inline engines (4-, 6-, and 8-cylinder) since 1903, but development of its first V8 began in 1944, and the new engine debuted in its 1953 cars following an accumulated million road-test miles. Buick stated that the was designed to "powerful, efficient, smooth, quiet, durable, and easily serviced", but need to be "realized with the lightest and most compact package which we could produce, consistent with minimum manufacturing cost". Other designs were abandoned because of space requirements. Buick’s move from inline engines to 90-degree V-engines created underhood clearance concerns, especially on the steering-gear side. The new engine’s oversquare design (0.8:1 stroke/bore ratio) and “vertical, in-line positioning of the valves”, however, minimized overall engine width. This, plus a one-inch increase in front tread in its new 1953 models, “permitted the continuation of all chassis improvements developed with the former in-line engine.”

Buick’s engine designers considered it necessary that combustion chambers have a centrally located spark plug, and their new V-8 was “more nearly centrally located than in any other American automobile engine.” Inline valves were retained from Buick’s inline-8cyl. in the 1953 V-8 “chiefly to make the engine more compact, to save weight, and to facilitate manufacture.” The new engine’s exhaust valve was smaller than in competitors’ large V-8s, and Buick stated that “a smaller valve opening earlier and higher can duplicate ... the opening area of a larger valve with the added advantage that flow efficiency is maintained by avoiding the sudden expansion into a large port” and "made a more compact combustion chamber possible, improved valve cooling, and reduced cost, without entailing any loss of power. The reduced valve weight brought the exhaust pump-up speed well above that of the inlet valve, thus providing insurance against exhaust valve breakage."

Compared to the then-current 300-plus cubic inch engines from Chrysler, and GM's other brands, Buick’s new powerplant was shorter, narrower, weighed less, and had a lighter crankshaft. The new engine was manufactured with compression ratios of 8:1 and 8.5:1, higher than 1953 Chrysler models.

The Buick V8 family can be divided into three groupings: "Nailheads", produced between 1953 and 1966, which came in two generations using different blocks in displacements from 264–425 cu in (4.3–7.0 L), and are known for their unique valve design and head configuration; "small blocks" produced from 1961 to 1982 in displacements from 215–350 cu in (3.5–5.7 L); and "big blocks" produced from 1967 to 1976 in displacements from 400–455 cu in (6.6–7.5 L).

The use of "small-block" and "big-block" terminology refers to the respective engine block's bore spacing, external dimensions, and weight, not internal engine displacement.

The "Nailhead" nickname derives from the unusually long, small valves of the original Buick V8, a function in part of the unusual horizontal positioning of the engine's heads.

Even though they are not generally held to be, by some important empirical measures, including a deck height that allowed displacement to grow to 425 cu in (7.0 L), the Buick "Nailhead" engines can be regarded as "big block" - a term that did not exist in that usage until exceptionally large displacement V8s with correspondingly large blocks began to appear and be distinguished from their more moderate-sized predecessors. The term "small-block" is a retronym, developed to distinguish engines with small and medium blocks from the very large block engines being introduced in response to increasing automobile size and the "horsepower wars" of the 1960s.