2000
#146,011
National surname rank
Recorded bearers 104
First available Census row
Per 100,000 0.04
Very Rare Last name
Riou
A surname derived from a place name in France.
According to the 2020 US Census Bureau surname tables, roughly 122 Americans carry the last name Riou. That puts it at #152,339 in the national surname ranking, appearing at a frequency of 0.04 per 100,000 people (about 1 in 2,809,462 residents).
This page is the full Name Census profile for the Riou surname. You will find the Census Bureau frequency data, a multi-census history view, an ancestry and ethnicity breakdown based on self-reported demographics, the name's meaning and origin where available, and answers to the most common questions people ask about this surname.
Bearers in the US
122
1 in 2,809,462
Census rank
#152,339
2020 decennial data
Per 100,000
0.0
Frequency rate
Recorded bearers
106
very rare in the US
Popularity narrative
The Census Bureau recorded 106 bearers of the surname Riou in its 2020 decennial surname file. At a rate of 0.04 per 100,000 residents, it holds the 152339th position in the national surname ranking.
Among Census respondents with the surname Riou, the largest self-reported group is White at 55.7%. The next largest groups are Black (29.2%) and Hispanic (7.5%).
Origin
Meaning and origin of Riou
The surname RIOU originated in France, specifically in the region of Poitou. It is derived from the Old French word "riu," which means "stream" or "river." This suggests that the name may have initially referred to someone who lived near a river or stream.
The earliest recorded instances of the name date back to the 12th century, where it was often spelled as "Riu" or "Ryu." One notable mention is in the Livre des Vassaux du Comté de Champagne, a manuscript from the late 12th century that listed feudal landholders in the region of Champagne.
In the 13th century, the name began to appear in various forms, such as "Ryou," "Riou," and "Rioux," reflecting the regional variations in pronunciation and spelling. During this time, the name was also associated with several place names in France, such as Riou-Martin and Riou-Blanc, further solidifying its connection to geographic features.
One of the earliest known bearers of the name was Jean Riou, a French nobleman who lived in the late 13th century and served as a knight in the court of King Philip IV of France. Another notable figure was Jeanne Riou, a 14th-century noblewoman who inherited significant landholdings in the Poitou region.
In the 15th century, the name gained prominence with the birth of Pierre Riou (1425-1492), a prominent merchant and landowner in the city of Bordeaux. His descendants continued to play influential roles in the region's commerce and governance over the following centuries.
During the 16th century, the name spread beyond France as French explorers and settlers ventured to other parts of the world. One notable bearer was Jean-Baptiste Riou (1543-1612), a French navigator who accompanied Jacques Cartier on his voyages to North America and helped establish settlements in what is now Canada.
In the 17th century, the name continued to be prominent in France, with several individuals bearing the surname achieving recognition in various fields. For example, Claude Riou (1622-1701) was a renowned French architect who designed several notable buildings in Paris, while Jean-Baptiste Riou (1677-1743) was a celebrated painter known for his portraiture and religious works.
As the name spread across generations and regions, it was further influenced by local dialects and spelling variations, resulting in forms such as "Rieux," "Rieu," and "Ryo." However, the core meaning and connection to geographic features remained consistent throughout its history.
Demographics
Ancestry and ethnicity for Riou
Among Census respondents with the surname Riou, the largest self-reported group is White at 55.7%. The next largest groups are Black (29.2%) and Hispanic (7.5%).
The bar chart below shows how Riou bearers described their own race and ethnicity on the 2020 Census form. The Census Bureau groups responses into six broad categories: White, Black or African American, Hispanic or Latino, Asian and Pacific Islander, American Indian and Alaska Native, and Two or More Races. When a category has too few respondents for a given surname, the Bureau suppresses the figure to protect individual privacy, which is why some names show fewer than six slices.
Percentages are shown for every Census year so the breakdown stays comparable over time. When the source file also includes raw headcounts, Name Census shows those alongside the percentages in the legend.
Keep in mind that these are self-reported numbers. A person's surname does not determine their race or ethnicity, and the distribution you see here reflects the specific population who happened to carry the Riou surname at the time of the 2020 Census, not any inherent property of the name itself.
- White55.7% · 59
- Black or African American29.2% · 31
- Hispanic or Latino7.5% · 8
- Asian and Pacific Islander7.5% · 8
Timeline
Historical Census data for Riou
Riou appears in 3 published Census surname files: 2000, 2010, 2020. The cards below show how the name's rank and bearer count changed across each release.
2010
#143,149
National surname rank
Recorded bearers 116
+12 bearers (+11.5%)
Per 100,000 0.04
Rank movement Up 2,862 places
2020
#152,339
National surname rank
Recorded bearers 106
-10 bearers (-8.6%)
Per 100,000 0.04
Rank movement Down 9,190 places
| Year | Rank | Count | Per 100K | Count change | Rank change |
|---|---|---|---|---|---|
| 2000 | #146,011 | 104 | 0.04 | First available Census row | First available Census row |
| 2010 | #143,149 | 116 | 0.04 | +12 bearers (+11.5%) | Up 2,862 places |
| 2020 | #152,339 | 106 | 0.04 | -10 bearers (-8.6%) | Down 9,190 places |
For 2020, the Census Bureau published race and Hispanic-origin columns as counts rather than percentages. Name Census converts those counts back into shares so the ancestry section stays comparable with the older surname files.
Year on year
2010 vs 2020 Census
How has the Riou surname changed between Census years? The chart shows bearer count side by side, and the table compares rank, count, and frequency.
Census year comparison
20102020
| Metric | 2010 | 2020 | Change |
|---|---|---|---|
| Rank | #143,149 | #152,339 | -6.4% |
| Count | 116 | 106 | -8.6% |
| Per 100K | 0.04 | 0.04 | -11.3% |
Between the 2010 and 2020 Census, the number of Riou bearers went from 116 to 106 (-8.6% change). The surname moved down 9,190 positions in the national ranking, going from #143,149 to #152,339.
FAQ
Riou surname: questions and answers
How many people in the U.S. have the surname Riou?
Name Census estimates that about 122 living Americans carry the surname Riou. Using the current population baseline, that works out to roughly 1 in 2,809,462 residents.
How common is Riou?
Riou ranks #152,339 in the 2020 Census surname tables and is classified on this site as "Very Rare." The Census recorded the name at a frequency of 0.04 per 100,000 residents, which is about 0 people out of every 100,000.
How many people with this surname were counted in the Census?
The raw 2020 Census file counted 106 people with the surname Riou. That is different from the site's living-bearer estimate (122), which projects the surname's present-day count by applying the Census frequency rate to the current U.S. population.
What does 0.04 per 100,000 actually mean?
It is the Census Bureau's normalized frequency measure. A rate of 0.04 per 100,000 means that if you picked a random group of 100,000 U.S. residents, you would expect about 0 of them to have the surname Riou.
Has Riou become more or less common over time?
Between 2010 and 2020, the surname Riou went from 116 recorded bearers to 106. That is a decrease of 10 (-8.6%). In the national ranking it fell from #143,149 to #152,339.
What does the Census say about the background of Riou?
Among Census respondents with the surname Riou, the largest self-reported group is White at 55.7%. The next largest groups are Black (29.2%) and Hispanic (7.5%). These figures come from the 2020 Census Bureau surname tables, based on how respondents described their own race and ethnicity.
Which group reports this surname most often?
White is the largest self-reported group for the surname Riou in the 2020 Census, accounting for 55.7% (59 people in the source table).
What is the full ancestry breakdown?
Riou appears across multiple self-reported groups in the Census data. The largest shares in the 2020 file are White (55.7%), Black (29.2%), Hispanic (7.5%). For 2020, the source file also published raw headcounts for each group, which is why this page can show both percentages and counts in the ancestry section.
Is this page using the latest Census data?
Yes. This page is using the latest surname file currently loaded on Name Census, which is 2020. The historical section above also keeps any older Census surname entries we have for Riou (2000, 2010, 2020).
Does the Census include every surname?
No. The Census Bureau only publishes surnames that appeared at least 100 times in a given decennial Census. That means very rare surnames are excluded entirely, and a surname can appear in one Census release but disappear from a later one if it falls below the reporting threshold.
Why don't the ancestry percentages always add up to exactly 100%?
There are two main reasons: rounding and suppression. The Census Bureau rounds published values, and it may suppress very small cells to protect privacy. For 2020, the Bureau also published raw group counts rather than direct percentages, so Name Census converts those counts back into shares for comparability across census years.
What does Riou mean?
A surname derived from a place name in France. The fuller origin note on this page goes into more detail.
Where does the surname data come from?
All surname statistics on Name Census are drawn from the US Census Bureau's decennial surname frequency tables. These files list every surname that appeared 100 or more times in the 2020 Census, along with a count, a per-100,000 rate, and a self-reported demographic breakdown. You can read the full explanation on our methodology page.
How does Name Census estimate living bearers?
For surnames, Name Census does not age cohorts the way it does for first names. Instead, it takes the Census Bureau's published frequency for Riou (0.04 per 100,000) and applies that rate to the current U.S. resident population to estimate how many living Americans have the surname today.
How many people are called Riou?
For a quick modern take, check how many Americans have the surname Riou on our sister site HowManyOfMe.org.