A pilaster, a word from the Italian pilastro,[1]​ is a pillar or column "Column (architecture)"), with a quadrangular base,[2]​ attached to a wall or wall. Its function may be structural, supporting the roof (construction), roof, entablature, molding or architrave, or merely decorative. The pilaster (word derived from pilar) can be composed of the same architectural elements as the columns or pillars, such as base, shaft and capital, according to the different architectural orders. When they protrude from the wall and are elongated and connected with blind arches, they are called Lombard bands.[1]​.

The first known stone pilasters were erected in the funerary complex of Pharaoh Dyeser (Zoser), in present-day Saqqara, Egypt, as a semi-decorative element, without losing their structural function, imitating grouped plant trunks - their immediate predecessor - as columns attached to the end of a wall. In Greek Architecture there are few examples of pilasters, because the structural elements configured the shape of the buildings. They were used extensively in the constructions of Ancient Rome.

A unique case of pilaster use occurs in Gothic Architecture, where the elements that supported the cross vaults were cruciform pillars (that is, in the shape of a cross seen in section). These pillars have this shape because it is a pillar that has a pilaster "attached" to each of its four faces, which is a continuation of the "nerve" of the corresponding arch, forming the whole this form of ribbed elements so characteristic of the Gothic.

As the decorative purpose of the pilasters was highly appreciated, they began to lose their supporting function, becoming more attached to the wall, even becoming embedded. This turning point was given, in general, in Renaissance Architecture, especially in the Cinquecento and Mannerism, and was used very widely in the Baroque, especially in facades and altars "Altar (religion)"). The proliferation of these in the Baroque gave rise to variants of the simple pilaster such as the stipe "Estípite (architecture)"), a pilaster or pillar whose trunk or shaft is in the shape of an inverted trunk of a pyramid "Pyramid (geometry)"), especially abundant in the Spanish Baroque.