Use an apostrophe in a surname only when it's part of a traditional or established spelling, such as O'Reilly or MacKenzie. The apostrophe does not indicate possession or pluralization-it marks a historical or linguistic contraction.
English-language surnames often include apostrophes due to Gaelic, Scottish, or Old English roots. These marks preserve pronunciation and lineage, not grammatical function. For example, "O'Donnell" comes from the Irish Ó Dónnghaile, where the "O'" signifies "descendant of." The apostrophe is not optional in such cases-it's part of the name's identity.
Many people incorrectly add apostrophes to surnames that don't require them. "Smith's" implies ownership, not identity. A person named Smith does not have a possessive form unless context demands it. The name itself remains "Smith," regardless of usage in a sentence.
Apostrophes in surnames follow phonetic and etymological logic, not standard English grammar rules. They appear in names derived from languages where elision (omission of a sound) was common. In Irish, for instance, the prefix "Ó" meant "descendant of" and evolved into "O'" in anglicized forms. The apostrophe preserves the original structure.
Names like "McCarthy" or "MacDonald" use "Mc" or "Mac" as prefixes meaning "son of." These are not abbreviations-they're inherited titles. The apostrophe in "O'Malley" or "O'Hara" separates the initial letter from the rest of the name, indicating a dropped vowel. Without it, the name would be misread or mispronounced.
When writing formal documents, always verify the correct spelling. The U.S. Social Security Administration lists "O'Neill" with an apostrophe, not "Oneill." The Associated Press Stylebook confirms that such names retain their apostrophes in print.
Not all surnames with apostrophes are the same. They fall into distinct categories based on origin and structure.
| Type | Origin | Examples | Rule |
|---|---|---|---|
| Irish O' names | Gaelic | O'Connor, O'Shea, O'Reilly | "O'" = "descendant of"; apostrophe required |
| Scottish Mac/ Mc names | Old Gaelic | MacArthur, McDonald, McPherson | "Mac" = "son of"; no apostrophe needed, though "Mc" is used |
| Irish Ó names | Gaelic | Ó Brien, Ó Flaherty | Anglicized as "O'" with apostrophe; original uses "Ó" with acute accent |
| French or Latin-derived names | Latin/French | D'Amato, d'Aubrey, de la Cruz | "d'" = "of the"; apostrophe indicates contraction; lowercase "d" in most cases |
Some names use apostrophes for phonetic clarity. "Fitzgerald" comes from "Fitz" (son of) + "Gerald." The "Fitz" is not abbreviated-it's a hereditary prefix. No apostrophe appears in "Fitzgerald," unlike "O'Reilly."
Non-English names with apostrophes are often miswritten in English contexts. "M'Coy" is incorrect-correct spelling is "McCoys." The apostrophe belongs to the original language's orthography, not a rule applied arbitrarily.
People frequently misuse apostrophes in surnames, especially in informal writing. "The Johnson's house" assumes the family owns the property-but the name "Johnson" is not possessive. The correct phrasing is "the Johnsons' house" when referring to the family collectively.
Another error: adding apostrophes to names that lack them. "Williams" is not "Willi'm's." The name is spelled "Williams" with no apostrophe. Adding one changes the spelling and may cause confusion in official records.
Even professional publications make errors. The New York Times corrected a headline that read "O'Reilly's column" when the subject was the person, not a possession. The correct reference is "O'Reilly's column," because the name is being used as a proper noun, not a possessive form.
One non-obvious fact: apostrophes in surnames are not capitalized unless they begin a sentence. "O'Hara" is correct; "O'hara" is not. The apostrophe is part of the name's spelling, not a standalone punctuation mark.
Consider the name "D'Angelo." This is a surname of Italian origin, derived from "di Angelo," meaning "of the angel." The apostrophe is essential-it reflects the contraction of "di" into "d'." Writing it as "DAngelo" or "D'Angelo" without the apostrophe alters the name's authenticity.
In formal correspondence, such as invitations or legal documents, the name must match the person's birth certificate. A wedding invitation reading "Mr. and Mrs. O'Reilly" is correct. "Mr. and Mrs. OReilly" is not.
I once attended a conference where a speaker's name was listed as "McCartney" on the program. The actual name was "McCartney" with a capital M and no apostrophe. After the event, I checked the attendee list-her name was correctly spelled "McCartney" in the registration system. The error came from assuming "Mc" implied an apostrophe. It does not.
For names like "de la Vega," the apostrophe is part of the Spanish naming convention. "De" means "of," and "la" means "the." The full name is "de la Vega," not "delavega." The apostrophe is necessary for accuracy and respect.
Names without apostrophes are far more common. Most English surnames-Smith, Brown, Jones-do not use apostrophes. Even names with similar sounds are spelled without them. "McKenna" is correct; "Mc'Kenna" is not.
When a surname appears in a possessive construction, the apostrophe goes after the entire name, not within it. "The Wilsons' car" is correct. "The Wilson's car" implies only one Wilson, which is inaccurate if referring to a family.
When citing multiple people, use the plural form. "The O'Reillys live in Dublin." "The O'Reillys' vacation photos were stunning." The apostrophe follows the "s" in the plural form, not inside the name.
Always verify surname spelling through official sources. The Library of Congress's Name Authority File includes standardized spellings for surnames with apostrophes. The Oxford English Dictionary provides etymological breakdowns for names like "O'Grady" and "MacLeod."
If you're unsure about a surname's spelling, consult the individual directly. A person's name is personal. Miswriting it-even with a misplaced apostrophe-can feel disrespectful.