A nobiliary particle is a type of onomastic particle used in a surname or family name in many Western cultures to signal the nobility of a family. The particle used varies depending on the country, language and period of time. In some languages, it is the same as a regular prepositional particle that was used in the creation of many surnames. In some countries, it became customary to distinguish the nobiliary particle from the regular one by a different spelling, although in other countries these conventions did not arise, occasionally resulting in ambiguity. The nobiliary particle can often be omitted in everyday speech or certain contexts.

In Denmark and Norway, there is a distinction between (1) nobiliary particles in family names and (2) prepositions denoting an individual person's place of residence.

Nobiliary particles like af, von, and de (English: of) are integrated parts of family names. The use of particles was not a particular privilege for the nobility. On the other hand, particles were almost exclusively used by and associated with them. Especially in the late 17th and 18th centuries, a person would often receive a particle along with his or her old or new family name when ennobled. Examples are families like de Gyldenpalm (lit. 'of Goldenpalm') and von Munthe af Morgenstierne (lit. 'of Munthe of Morningstar'). Otherwise, particles would arrive together with immigrants. Examples are families like von Ahnen. Prominent non-noble families having used particles are von Cappelen, von der Lippe, and de Créqui dit la Roche.

The preposition til (English: to, but translates as of; comparable with German zu) is placed behind a person's full name in order to denote his or her place of residence, for example Sigurd Jonsson til Sudreim.

In France—and in England, largely as a result of the Norman Conquest—the particle de precedes a nom de terre ('name of land') in many families of the French nobility: for example, Maximilien de Béthune. A few do not have this particle: for example, Pierre Séguier, Lord Chancellor of France. The particle can also be du ('of the' in the masculine form), d' (used, per the rules of orthography, when the nom de terre begins with a vowel; for example, Ferdinand d'Orléans), or des ('of the' in the plural). In French, de indicates a link between the land and a person—either landlord or peasant.

The nobleman was always designated escuyer, for 'squire' in English form (dapifer in Latin), or chevalier for 'knight' (equites in Latin). Only knights were designated by the spoken style monseigneur or messire for 'sir' (dominus in Latin), as, for example, "monseigneur Bertrand du Guesclin, chevalier"—in English form, "Sir Bertrand du Guesclin, knight".

By convention, surnames with the non-noble use of the particle de are spelled as a single word (e.g., "Pierre Dupont"), though many such surnames conserved the de as a separate word.

Since the sixteenth century, surnames among the French nobility have often been composed of a combination of patronymic names, titles, or noms de terres ('names of lands' or estates) joined by the preposition de, as in "Charles Maurice de Talleyrand-Périgord". The use of this particle began to be an essential appearance of nobility. Following the end of the Kingdom of France, however, the use of de did not invariably denote nobility. In the eighteenth and nineteenth centuries, some middle-class families simply adopted the particle without being ennobled; Maximilien Robespierre's family, for example, used the particle for some generations.