The apostrophe in "Happy Mother's Day" causes genuine confusion every May. Cards, email subject lines, social posts, and official proclamations all handle it differently, and that inconsistency makes the right answer feel elusive. It isn't. The apostrophe belongs in "Mother's Day," and it belongs in a specific spot: after the r and before the s, giving you Mother's Day, not Mothers' Day and not Mothers Day.
Why the apostrophe goes after "Mother" and not after "Mothers"
Possessive apostrophes mark a relationship between a noun and what follows it. The question is whether that relationship belongs to one mother or to many. Anna Jarvis, who campaigned to establish Mother's Day as an official U.S. holiday in the early 1900s, was deliberate on this point: she wanted the day to honor each individual mother, not mothers as a collective. The holiday is a personal celebration between a child and their mother, not a group tribute to motherhood in general.
That original intent is exactly why the possessive is singular. "Mother's Day" literally means "the day belonging to (your) mother." Writing Mothers' Day shifts the meaning to a day belonging to all mothers collectively, which was not Jarvis's intention and is not the name of the holiday as it's officially recorded in the United States.
The U.S. Congress codified the holiday in 1914 using the singular possessive, and that spelling has been the official form ever since. Style guides including AP Stylebook follow that same convention.
The three versions you'll see, and which one is correct
Writers produce three forms in the wild. Only one is standard.
- Mother's Day: singular possessive. Correct. This is the official name of the holiday.
- Mothers' Day: plural possessive. Grammatically defensible but factually wrong as the holiday's name.
- Mothers Day: no apostrophe at all. An error, full stop.
The no-apostrophe version is the most common mistake, mostly because people treat "Mothers" as a simple modifier rather than a possessive noun. It isn't. "Mother's Day" follows exactly the same pattern as "Valentine's Day" or "St. Patrick's Day." Drop the apostrophe from any of those and you've dropped part of the name.
What about Father's Day and other similar holidays?
The logic is identical. "Father's Day" takes a singular possessive apostrophe for the same reasons: one father, one child, one day. "Parents' Day," however, uses the plural possessive because the holiday is designed to honor both parents jointly, so the apostrophe moves to after the s. The underlying principle is consistent: identify whether the possessive relationship is singular or plural, then place the apostrophe accordingly.
This is the same rule that governs trickier cases in professional writing. If you find these possessive distinctions useful, the deeper guide to more apostrophe rules covers the patterns that trip up even experienced writers.
Using the phrase correctly in business writing
Business writers encounter "Mother's Day" in email subject lines, retail promotions, social media copy, and cards sent on behalf of an organization. The rule doesn't change based on medium. Write Mother's Day every time.
A few practical points for professional contexts:
- Capitalize both words. "Mother's Day" is a proper noun (the name of a holiday), so both Mother and Day take a capital letter.
- Don't italicize or quote it. It's a standard proper noun, not jargon.
- In a subject line like "Happy Mother's Day from the team at [Company]," the apostrophe is fully visible and correct. Don't omit it for the sake of brevity.
One more thing worth noting: "happy" in "Happy Mother's Day" is an adjective modifying the greeting, not part of the holiday's proper name. You'd capitalize it at the start of a sentence or when using the full phrase as a standalone greeting, but it's lowercase when embedded mid-sentence: "We wanted to wish all our clients a happy Mother's Day this year."
A quick memory check
If you ever draw a blank, ask yourself: whose day is it? It's your mother's day. One mother, one day. Singular possessive. The apostrophe goes between the r and the s.
That test works reliably for Father's Day, Valentine's Day, and any other holiday built on the same possessive structure. It's also the same logic behind knowing whether to write "master's degree" or "masters degree": possessive apostrophes follow the relationship, not the sound of the word.
Write "Mother's Day." Skip "Mothers' Day." Never drop the apostrophe entirely. That's the complete rule.